Source Code Management wih git Matthieu Herrb December 2019 https://homepages.laas.fr/matthieu/cours/pi2-git.pdf
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Source Code Management wih git
Matthieu Herrb
December 2019
httpshomepageslaasfrmatthieucourspi2-gitpdf
License
This work is licensed under a Creative Commons Attribution-ShareAlike 30 UnportedLicenseTo get a copy of the license use the following addresshttpcreativecommonsorglicensesby-sa30
December 2019 284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 484
WTF is a version control system
Software that manages history of changes in a set of documents
Typically source code
But alsodocumentationweb sitesconfiguration filesetc
December 2019 584
Basic functionalities
keep an history of changesmake it possible to work in teamsallow parallel workprovide security (integrity availability confidentiality)
December 2019 684
Diff amp patch
patch
patch
V2 V1 V1
V2
-+
December 2019 784
Merge
Applying a patch to a slightly different version
patch
patch
V2 V1 Vn
Vn+1
- +
May fail rarr conflictDecember 2019 884
Text diff
A patch represents the changes between 2 versions of a text file
diff -u produces a patch--- asrcserverc+++ bsrcserverc -2227 +2229 reset_log(void)ifdef HAVE_SS_LENdefine sockaddr_len(s) sss_lenelse-define sockaddr_len(s) sizeof(s)+define sockaddr_len(s) (sss_family == AF_INET6 + sizeof(struct sockaddr_in6) + sizeof(struct sockaddr_in))endif
void
December 2019 984
The patch command
patch applies a patch to a file to produce the new version
Example patch -p1 -E lt diff
patch can handle small inconsistencies thanks to the context
December 2019 1084
Version Control concepts (1)
RepositoryStorage area that keeps the history of modificationsRevisionUnique identifier of Each state of the source filesAlso called commit as language shortcut
A B C
Ordered sequence arrows point to the ancestor
rarr Marketing project version = VCS revision
December 2019 1184
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
License
This work is licensed under a Creative Commons Attribution-ShareAlike 30 UnportedLicenseTo get a copy of the license use the following addresshttpcreativecommonsorglicensesby-sa30
December 2019 284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 484
WTF is a version control system
Software that manages history of changes in a set of documents
Typically source code
But alsodocumentationweb sitesconfiguration filesetc
December 2019 584
Basic functionalities
keep an history of changesmake it possible to work in teamsallow parallel workprovide security (integrity availability confidentiality)
December 2019 684
Diff amp patch
patch
patch
V2 V1 V1
V2
-+
December 2019 784
Merge
Applying a patch to a slightly different version
patch
patch
V2 V1 Vn
Vn+1
- +
May fail rarr conflictDecember 2019 884
Text diff
A patch represents the changes between 2 versions of a text file
diff -u produces a patch--- asrcserverc+++ bsrcserverc -2227 +2229 reset_log(void)ifdef HAVE_SS_LENdefine sockaddr_len(s) sss_lenelse-define sockaddr_len(s) sizeof(s)+define sockaddr_len(s) (sss_family == AF_INET6 + sizeof(struct sockaddr_in6) + sizeof(struct sockaddr_in))endif
void
December 2019 984
The patch command
patch applies a patch to a file to produce the new version
Example patch -p1 -E lt diff
patch can handle small inconsistencies thanks to the context
December 2019 1084
Version Control concepts (1)
RepositoryStorage area that keeps the history of modificationsRevisionUnique identifier of Each state of the source filesAlso called commit as language shortcut
A B C
Ordered sequence arrows point to the ancestor
rarr Marketing project version = VCS revision
December 2019 1184
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 484
WTF is a version control system
Software that manages history of changes in a set of documents
Typically source code
But alsodocumentationweb sitesconfiguration filesetc
December 2019 584
Basic functionalities
keep an history of changesmake it possible to work in teamsallow parallel workprovide security (integrity availability confidentiality)
December 2019 684
Diff amp patch
patch
patch
V2 V1 V1
V2
-+
December 2019 784
Merge
Applying a patch to a slightly different version
patch
patch
V2 V1 Vn
Vn+1
- +
May fail rarr conflictDecember 2019 884
Text diff
A patch represents the changes between 2 versions of a text file
diff -u produces a patch--- asrcserverc+++ bsrcserverc -2227 +2229 reset_log(void)ifdef HAVE_SS_LENdefine sockaddr_len(s) sss_lenelse-define sockaddr_len(s) sizeof(s)+define sockaddr_len(s) (sss_family == AF_INET6 + sizeof(struct sockaddr_in6) + sizeof(struct sockaddr_in))endif
void
December 2019 984
The patch command
patch applies a patch to a file to produce the new version
Example patch -p1 -E lt diff
patch can handle small inconsistencies thanks to the context
December 2019 1084
Version Control concepts (1)
RepositoryStorage area that keeps the history of modificationsRevisionUnique identifier of Each state of the source filesAlso called commit as language shortcut
A B C
Ordered sequence arrows point to the ancestor
rarr Marketing project version = VCS revision
December 2019 1184
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 484
WTF is a version control system
Software that manages history of changes in a set of documents
Typically source code
But alsodocumentationweb sitesconfiguration filesetc
December 2019 584
Basic functionalities
keep an history of changesmake it possible to work in teamsallow parallel workprovide security (integrity availability confidentiality)
December 2019 684
Diff amp patch
patch
patch
V2 V1 V1
V2
-+
December 2019 784
Merge
Applying a patch to a slightly different version
patch
patch
V2 V1 Vn
Vn+1
- +
May fail rarr conflictDecember 2019 884
Text diff
A patch represents the changes between 2 versions of a text file
diff -u produces a patch--- asrcserverc+++ bsrcserverc -2227 +2229 reset_log(void)ifdef HAVE_SS_LENdefine sockaddr_len(s) sss_lenelse-define sockaddr_len(s) sizeof(s)+define sockaddr_len(s) (sss_family == AF_INET6 + sizeof(struct sockaddr_in6) + sizeof(struct sockaddr_in))endif
void
December 2019 984
The patch command
patch applies a patch to a file to produce the new version
Example patch -p1 -E lt diff
patch can handle small inconsistencies thanks to the context
December 2019 1084
Version Control concepts (1)
RepositoryStorage area that keeps the history of modificationsRevisionUnique identifier of Each state of the source filesAlso called commit as language shortcut
A B C
Ordered sequence arrows point to the ancestor
rarr Marketing project version = VCS revision
December 2019 1184
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
WTF is a version control system
Software that manages history of changes in a set of documents
Typically source code
But alsodocumentationweb sitesconfiguration filesetc
December 2019 584
Basic functionalities
keep an history of changesmake it possible to work in teamsallow parallel workprovide security (integrity availability confidentiality)
December 2019 684
Diff amp patch
patch
patch
V2 V1 V1
V2
-+
December 2019 784
Merge
Applying a patch to a slightly different version
patch
patch
V2 V1 Vn
Vn+1
- +
May fail rarr conflictDecember 2019 884
Text diff
A patch represents the changes between 2 versions of a text file
diff -u produces a patch--- asrcserverc+++ bsrcserverc -2227 +2229 reset_log(void)ifdef HAVE_SS_LENdefine sockaddr_len(s) sss_lenelse-define sockaddr_len(s) sizeof(s)+define sockaddr_len(s) (sss_family == AF_INET6 + sizeof(struct sockaddr_in6) + sizeof(struct sockaddr_in))endif
void
December 2019 984
The patch command
patch applies a patch to a file to produce the new version
Example patch -p1 -E lt diff
patch can handle small inconsistencies thanks to the context
December 2019 1084
Version Control concepts (1)
RepositoryStorage area that keeps the history of modificationsRevisionUnique identifier of Each state of the source filesAlso called commit as language shortcut
A B C
Ordered sequence arrows point to the ancestor
rarr Marketing project version = VCS revision
December 2019 1184
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Basic functionalities
keep an history of changesmake it possible to work in teamsallow parallel workprovide security (integrity availability confidentiality)
December 2019 684
Diff amp patch
patch
patch
V2 V1 V1
V2
-+
December 2019 784
Merge
Applying a patch to a slightly different version
patch
patch
V2 V1 Vn
Vn+1
- +
May fail rarr conflictDecember 2019 884
Text diff
A patch represents the changes between 2 versions of a text file
diff -u produces a patch--- asrcserverc+++ bsrcserverc -2227 +2229 reset_log(void)ifdef HAVE_SS_LENdefine sockaddr_len(s) sss_lenelse-define sockaddr_len(s) sizeof(s)+define sockaddr_len(s) (sss_family == AF_INET6 + sizeof(struct sockaddr_in6) + sizeof(struct sockaddr_in))endif
void
December 2019 984
The patch command
patch applies a patch to a file to produce the new version
Example patch -p1 -E lt diff
patch can handle small inconsistencies thanks to the context
December 2019 1084
Version Control concepts (1)
RepositoryStorage area that keeps the history of modificationsRevisionUnique identifier of Each state of the source filesAlso called commit as language shortcut
A B C
Ordered sequence arrows point to the ancestor
rarr Marketing project version = VCS revision
December 2019 1184
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Diff amp patch
patch
patch
V2 V1 V1
V2
-+
December 2019 784
Merge
Applying a patch to a slightly different version
patch
patch
V2 V1 Vn
Vn+1
- +
May fail rarr conflictDecember 2019 884
Text diff
A patch represents the changes between 2 versions of a text file
diff -u produces a patch--- asrcserverc+++ bsrcserverc -2227 +2229 reset_log(void)ifdef HAVE_SS_LENdefine sockaddr_len(s) sss_lenelse-define sockaddr_len(s) sizeof(s)+define sockaddr_len(s) (sss_family == AF_INET6 + sizeof(struct sockaddr_in6) + sizeof(struct sockaddr_in))endif
void
December 2019 984
The patch command
patch applies a patch to a file to produce the new version
Example patch -p1 -E lt diff
patch can handle small inconsistencies thanks to the context
December 2019 1084
Version Control concepts (1)
RepositoryStorage area that keeps the history of modificationsRevisionUnique identifier of Each state of the source filesAlso called commit as language shortcut
A B C
Ordered sequence arrows point to the ancestor
rarr Marketing project version = VCS revision
December 2019 1184
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Merge
Applying a patch to a slightly different version
patch
patch
V2 V1 Vn
Vn+1
- +
May fail rarr conflictDecember 2019 884
Text diff
A patch represents the changes between 2 versions of a text file
diff -u produces a patch--- asrcserverc+++ bsrcserverc -2227 +2229 reset_log(void)ifdef HAVE_SS_LENdefine sockaddr_len(s) sss_lenelse-define sockaddr_len(s) sizeof(s)+define sockaddr_len(s) (sss_family == AF_INET6 + sizeof(struct sockaddr_in6) + sizeof(struct sockaddr_in))endif
void
December 2019 984
The patch command
patch applies a patch to a file to produce the new version
Example patch -p1 -E lt diff
patch can handle small inconsistencies thanks to the context
December 2019 1084
Version Control concepts (1)
RepositoryStorage area that keeps the history of modificationsRevisionUnique identifier of Each state of the source filesAlso called commit as language shortcut
A B C
Ordered sequence arrows point to the ancestor
rarr Marketing project version = VCS revision
December 2019 1184
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Text diff
A patch represents the changes between 2 versions of a text file
diff -u produces a patch--- asrcserverc+++ bsrcserverc -2227 +2229 reset_log(void)ifdef HAVE_SS_LENdefine sockaddr_len(s) sss_lenelse-define sockaddr_len(s) sizeof(s)+define sockaddr_len(s) (sss_family == AF_INET6 + sizeof(struct sockaddr_in6) + sizeof(struct sockaddr_in))endif
void
December 2019 984
The patch command
patch applies a patch to a file to produce the new version
Example patch -p1 -E lt diff
patch can handle small inconsistencies thanks to the context
December 2019 1084
Version Control concepts (1)
RepositoryStorage area that keeps the history of modificationsRevisionUnique identifier of Each state of the source filesAlso called commit as language shortcut
A B C
Ordered sequence arrows point to the ancestor
rarr Marketing project version = VCS revision
December 2019 1184
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
The patch command
patch applies a patch to a file to produce the new version
Example patch -p1 -E lt diff
patch can handle small inconsistencies thanks to the context
December 2019 1084
Version Control concepts (1)
RepositoryStorage area that keeps the history of modificationsRevisionUnique identifier of Each state of the source filesAlso called commit as language shortcut
A B C
Ordered sequence arrows point to the ancestor
rarr Marketing project version = VCS revision
December 2019 1184
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Version Control concepts (1)
RepositoryStorage area that keeps the history of modificationsRevisionUnique identifier of Each state of the source filesAlso called commit as language shortcut
A B C
Ordered sequence arrows point to the ancestor
rarr Marketing project version = VCS revision
December 2019 1184
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Version Control concepts (2)
Branches
A B C D I J
E F
G
H K
December 2019 1284
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches usage
Branches can be used to fix a bug in an released versiondevelop new ideas in parallelmanage a customized version of the softwaremerge back a version that diverged for some reasontrack local modifications to externally maintained sources
December 2019 1384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 1484
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
GIT
Distributed version control systemby opposition to CVS or SVN which are CentralizedDeveloped by Linus Torvalds for the Linux kernelSimilar to Monotone Darcs Mercurial Bazaar etc
December 2019 1584
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Git concepts (1)
repository all the history of the projectstored in the git directory
diff or patch differences between 2 versions of a filecommit (verb) action to register a version of a set of files
to the repositorycommit (noun) the result of a commit action represented by
a 128 hexadecimal SHA-1 hashbranch one line of development
by default all development is done in mastertag a symbolic identifier for a commit or a branch
December 2019 1684
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Git concepts (2)
Working tree the set of files being worked on currentlyIndex an object tracking modified added removed filesBlob binary data used to store files objects and other data
December 2019 1784
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Git Interfaces
Command lineGit GUIs
gitk (part of git distribution)gitg (Gnome project)git-cola httpgit-colagithubcomTortoiseGit (Windows)httpcodegooglecomptortoisegit
Editor pluginsAtom (built-in)Visual Studio Code(built-in)Eclipse (httpeclipseorgegit)Emacs (VC magit)
Web browsers cgit gitweb
December 2019 1884
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Git forges
Web sites dedicated to git projects hostinggithub httpsgithubcomgitlab httpsgitlabcomgogs httpsgogsioredmine with the git plugin
Include interesting features for collaboration
Better suited for distributed development than traditionalcentralized forges
December 2019 1984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 2084
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Initial setup
Sets defaults for commit messagesuser name amp emailpreferred text editor
$ git config --global --add username Matthieu Herrb$ git config --global --add useremail ltmatthieuherrblaasfrgt$ git config --global --add coreeditor emacs -nw
$ cat ~gitconfig[user]
name = Matthieu Herrbemail = ltmatthieuherrblaasfrgt
[core]editor = emacs -nw
December 2019 2184
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Creating a repository
git init creates an empty repository in the current directory$ mkdir git-tutorial$ cd git-tutorial$ git initInitialized empty Git repository in homemhgit-tuturialgit$ ls -l gittotal 24-rw-r--r-- 1 mh mh 23 Oct 26 0914 HEAD-rw-r--r-- 1 mh mh 111 Oct 26 0914 config-rw-r--r-- 1 mh mh 58 Oct 26 0914 descriptiondrwxr-xr-x 12 mh mh 408 Oct 26 0914 hooksdrwxr-xr-x 3 mh mh 102 Oct 26 0914 infodrwxr-xr-x 4 mh mh 136 Oct 26 0914 objectsdrwxr-xr-x 4 mh mh 136 Oct 26 0914 refs
December 2019 2284
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Adding files
git add adds new or modified files to the index$ echo Hello World gt filetxt$ git add
December 2019 2384
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Querying status
Shows the status of the repository and the index$ git status On branch master Initial commit Changes to be committed (use git rm --cached ltfilegt to unstage) new file filetxt
December 2019 2484
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Committing changes
$ git commitCreated initial commit 0ba7bd8 Initial version1 files changed 1 insertions(+) 0 deletions(-)create mode 100644 filetxt$ echo Hello Matthieu gt filetxt$ git commit -aCreated commit 7fbf4cb Modif1 files changed 1 insertions(+) 1 deletions(-)
Opens a text editor to enter a commit messageand commits the change to the repository
December 2019 2584
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
The git index
Represents modifications pending commit2 stages
1 add modified files to the index (addrm)2 ldquoflushrdquo the index to the repository (commit)
Short-cuts chaining both operationsgit commit filegit commit dir (or git commit )git commit -a
December 2019 2684
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Commits
Adds a node at the end of the current branch
A B C
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Commits
Adds a node at the end of the current branch
A B C D
Includesthe patch from old to new revision for text filesthe full new revision for binary filesattributes of the committed file (access modes)name and e-mail address of the committera log messageoptionally a digital signature
December 2019 2784
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Interactive add
$ git add -p [files]
Enters an interactive session to pick up changes to be added tonext commit
Allows to have several unrelated un-committed modifications andstill do clean separate commits
December 2019 2884
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Looking back git log
Various ways to display the history of modifications$ git logcommit 7fbf4cb7c8977061fbfb609016f5414e833a3a1cAuthor Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122933 2014 +0100
Modif
commit 0ba7bd8b93ef9ddd8917814bde8cbdaaf9732559Author Matthieu Herrb ltmatthieuherrblaasfrgtDate Tue Oct 28 122838 2014 +0100
Initial version$ git log --stat$ git log -p
December 2019 2984
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Examining changes git diff
Display the changes between the working files and the indexor between the index and the repositoryecho Good bye gt filetxt$ git diffdiff --git afiletxt bfiletxtindex 6bd8f3cc0ee9ab 100644--- afiletxt+++ bfiletxt -1 +1 -Hello Matthieu+Good bye$ git add filetxt$ git diff --cached
December 2019 3084
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Marking a version git tag
Create a tag object containing a name and a commentOpens the text editor to enter the comment$ git tag -a git-tuto-10$ git tag -lgit-tuto-10
December 2019 3184
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Fixing mistakes reverting to a good version
Restore the working dir to a given committed versionloosing all local changes$ git reset --hard [commit-id]
If commit-id is missing defaults to HEAD
Revert a given commit$ git revert 03baceFinished one revertCreated commit c333ab5 Revert 3rd version1 files changed 1 insertions(+) 1 deletions(-)
December 2019 3284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 3384
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches
A B C
masterExisting history
Branch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches
A B C
master
mybranch
Existing historyBranch creation
commits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches
A B C
master
D
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches
A B C
master
D E
mybranch
Existing historyBranch creationcommits in the new branch
commits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches
A B C
D E
mybranch
F
masterExisting historyBranch creationcommits in the new branchcommits in master
merge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches
A B C
D E
mybranch
F G
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into master
further commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches
A B C
D E
F G
master
H
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branch
etc
December 2019 3484
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches
A B C
D E
F G
master
H I
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches
A B C
D E
F G
H I
mybranch
J
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches
A B C
D E
F G
H I
mybranch
J K
masterExisting historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Branches
A B C
D E
F G
H I
J K
master
L
mybranch
Existing historyBranch creationcommits in the new branchcommits in mastermerge the branch into masterfurther commits in the branchetc
December 2019 3484
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Switching branches
Create a new branch$ git checkout -b newbranch
Switch back to master$ git checkout master
December 2019 3584
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Listing available branches
$ git branch masternewbranch
December 2019 3684
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Merging changes from another branch
$ git merge branch
Merge commits from ldquobranchrdquo and commits the result
2 kinds of mergesfast forward no conflicts only new commits to add to yourversionnormal merge there are local changes - use a 3 way mergealgorithm
December 2019 3784
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Handling conflicts
Conflicts happen when changes in a merged branch areincompatible with changes in the target branch
Files with conflicts contain conflict markersThey are not automatically added to the index
To proceed Resolve the conflict (ie choose the correct version)Add the manually merged files to the indexCommit the result
December 2019 3884
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Tools to help with merge
To solve conflicts git can use existing tools to help mergingmeld xxdiff opendiff DiffMerge
$ git config --global mergetool meld
$ git mergetool
December 2019 3984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 4084
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Working in teams
No locks on source codeEach developer has its own copy of the source and repositoryConflicts handling
First merge other peoplersquos contributionAutomated merges as much as possibleConflict detection rarr manual resolutionNo new commit before solving the conflict
December 2019 4184
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Centralized model
Pull
Pull
Push
Anne
Bernard Carole
Denis
Central repository
PullPull
Push
December 2019 4284
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Semi-Distributed model
Commit
Commitpull
pushpull
Geacuterard
pull
push
pull
Fabienne
Commit
pullHeacutelegravene
EricDecember 2019 4384
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Copying a repository
git clone repo
repo an url to the remote repository Can bea pathname to a local repository on the same file-systemssh[user]hostpath - use SSH with given usersshgithostpath - SSH with pubkey authentification(github redmine)githostpath - anonymous access with the GIT protocolhttpshostpath - anonymous access with HTTPSprotocol
December 2019 4484
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Remote repository
Remote repo A B C D master
December 2019 4584
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Remote repository
Remote repo A B C D master
Local repo A B C D originmaster
master
clone
December 2019 4584
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Updating from a remote repository
$ git pull
Pulls the remote branches to the local repositorymerges the default remote branch into the current one(Including commit)Can produce a conflict
Solve the conflictCommit the result
December 2019 4684
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Using rebase with remote repositories
git fetch fetches remote commits without merging them
Fetch and rebase at once$ git pull --rebase
equivalent to$ git fetch$ git rebase originmaster
December 2019 4784
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Remote branches
$ git branch -r
lists remote branches (originbranch)
Remote branches can be tracked (automatically mergedpushed)using$ git checkout -t -b newbranch originnewbranch
December 2019 4884
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Sending changes to a repository
$ git push
Sends local commits to remote tracked branchesProduces an error if not up-to-date (need to pull or rebase first)
Tags need to be pushed separately$ git push --tags
December 2019 4984
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 5084
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Git work flows
Work flows that help maintaining a consistent central masterbranchDevelopers use private repositoriesSeveral models of workflow exist using several tools
e-mail git send-email git amForge-provided tools (example Github pull request)Direct access to the private repositories
In all cases branches in the private repository allow to work onseveral changes until they are accepted
December 2019 5184
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Maintainer pull request work flow
Only the maintainer can push to masterDevelopers submit pull requests to the maintainerThe maintainer reviews merges and then pushes the result
December 2019 5284
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Pull requests
MarieEtienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
pu
ll requ
est
commit
clone
pull
merge
❶❷
❸
❹ ❺
❻
❼
❽
December 2019 5384
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Pull requests
Marie is the maintainer Dominique a developer and Etienne anend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Dominique sends a pull request to Marie5 Marie merges the pull request in her local repository6 Marie checks Dominiquersquos work7 If Marie is happy with the result pushes it to the main
repository8 Etienne can grab the result
December 2019 5484
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Reviews work flow
Push to master is openbut no one can push to master without a reviewDevelopers ask others for reviewsReviewers reply with an rsquoOK rsquoDeveloper amends the commit message to add rsquoReviewed-byrsquoheaders and pushes the result
December 2019 5584
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Reviews
Reacutegine Etienne
Dominique
gitopenrobotsorg
redminelaasfr
clone
pushpu
ll
push
clon
epu
ll
review req
uest
commit
reviewed
-by
clonepull
❶❷
❸
❹ ❺❻
❼
❽
December 2019 5684
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Reviews
Regine is a reviewer Dominique a developer and Etienne theend-user
1 Dominique clones the repository2 Dominique works on the code does some commit(s)3 Dominique pushes his commits to his private repository4 Doninique sends a review request to the community5 Regine picks up the request6 Regine accepts the change and sends a reviewed-by message
to Dominique7 Dominque amends his commit and pushes it to the main
repository8 Etienne can grab the result
December 2019 5784
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Using email
For small changes (patches) using email to interact withreviewersmaintainers is easierfaster
configure sendemailsmtpserver andsendemailsmtpuseruse git format-patch to generate the patches for thecommits to submit for review pulluse git send-email to send an email containing the patchesgenerated abovethe maintainer or reviewer can use git am to apply patchesfrom his mail client
See The advantages of an email-driven git workflow for moreinformation
December 2019 5884
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Managing remote repositories
git remote command
add name url add a remoteset-url name url changes the urlrename old new renamesrm name removes a remote
December 2019 5984
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Pushing to multiple remote repositories
git push remote branch push a given branch to a given remote
Example$ git push origin master same as git push$ git push github mybranch push branch to github
December 2019 6084
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6184
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Stashing local changes
Git refuses to merge a branch if there are un-commited changes
Solutionscommit local changes before mergingor stash local changes before merging
$ git stash$ git merge mybranch or git pull --rebase$ git stash pop
Itrsquos also possible to create a new branch with the stashed changes$ git stash branch newbranch
December 2019 6284
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Picking individual changes
Take one commit from another branch (bug fix)and apply it to the working branch
$ git cherry-pick SHA1_HASH
December 2019 6384
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Replaying changes from a branch
Merges create lots of unwanted links in the git data graphWhen a branch has only few local commits rebase is moreefficient
$ git rebase master
Only use rebase before pushing to a remote repository
December 2019 6484
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Rebase
A B
Existing commits
Development branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Rebase
A B
C D E
Existing commitsDevelopment branch
Commits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Rebase
A B
C D E
F G
Existing commitsDevelopment branchCommits in master
Start of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Rebase
A B F G
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branch
End of rebase recreate commits starting from HEAD demaster
December 2019 6584
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Rebase
A B F G
Crsquo Drsquo Ersquo
Existing commitsDevelopment branchCommits in masterStart of rebase remove commits from the branchEnd of rebase recreate commits starting from HEAD demaster
December 2019 6584
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Interactive rebase
Useful to re-arrange commits locally in order to clean up thehistory$ git rebase -i COMMITS
rarr opens a text editor with the list of commits specifiedRearrange the list according to instructions and save itrarr history will be re-written following the new list
Only use rebase before pushing to a remote repository
December 2019 6684
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
ldquoTreeishrdquo
Alternative ways to refer to objects or ranges of objectsfull sha-1 8f8aca4bd6c29048636966247aa582718559d871partial sha-1 8f8aca4b 8f8aca 8f8acbranch or tag name v10 master origintestingdate spec masteryesterday master1 month agoordinal spec master5carrot parent master^2tilde spec master~2tree pointer master^treeblob spec masterpathtofileranges 4c032a8faca4
See gitrevisions(1)December 2019 6784
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Examples
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Examples
master^
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Examples
master^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Examples
master~2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Examples
master~2^2 or master^^^2
18cae 2fbb3 4eadf 2f45e ce0e4 5ec47
c36ae df2fa a09c6 b3be1
master
December 2019 6884
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 6984
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Good practices - repositories
Do not abuse git as a generic cloud storageGit is good with text format files (source codeMarkdownLaTeX doccuments )Git is not useful on images PDF or Office documentsLarge binary files are wasting resources in a git repository
Keep repositories on topicOne repository per projectDo not store un-related files
Keep repository clean and minimaldo not add editor backup filesdo not add files that can be generated automaticallydo not add alternative versions as separate files Use branches
December 2019 7084
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Good practices - commits
Good commitss are hard but add a lot of value to the projectAlways provide informative commit messagesFollow the git commit convention
one line summaryone empty linedetailled information below (multiple lines)
Keep commits small and focusedDonrsquot blindly add changes Use git status and git diff toreview themUse git add -p to break-up large uncommited changes
Commit early and commit oftenUse amend or rebase to fix broken commits before pushing
December 2019 7184
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Good practices - branches
Keep the number of active branches smallUse self-documenting branches namesPrefer rebase to merge whenever possibleTry to keep a linear history on the main branch
December 2019 7284
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Good practices - distributed development
Ask for reviewsReview the patches that are sent to youAlways use pull --rebase when possible before pushingDo not push experimentaltest branches if not neededBe careful to push to the correct branchIn case of a mistake communicate with other developers
December 2019 7384
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 7484
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Identifying authors
$ git blame -- filetxt
for each line of the file shows the id and author of the lastmodification
December 2019 7584
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Making a release with git
(Alternative to automakersquos make dist)Commit all changes including the new macro revision numberTag the resultUse archive to produce a release
$ git tag -a foo-13$ git archive --prefix=foo-13 foo-13 | gzip -c - gt foo-13targz
December 2019 7684
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Binary search of bugs
$ git bisect start$ git bisect bad Current version is bad$ git bisect good v26-rc2 v26-rc2 was the last version
tested that was good$ git bisect reset back to initial state
With a script that can tell if the current code is good or bad$ git bisect run my_script arguments
my_script returns 0 rarr goodmy_script returns 1124 rarr bad
December 2019 7784
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Reflog
reflog is the safety net of gitrecords all changes done in the repositorykeeps track of commits not otherwise accessible anymoreallows to recover from some mistakeslocal only and expires after 90 days
Example$ git add footxt$ git commit$ git reset --hard ltolder versiongt OOPS $ git reflog$ git checkout HEADn
December 2019 7884
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Sub-modules
Sub-modules provide a way to glue several existing repositories intoa bigger project
git submodule add url pathadds a submodule at pathgit submodule initinit the sub-modulesgit submodule updateclone or pull the submodulesgit submodule statusdisplay information about submodule status
December 2019 7984
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
git-lfs Large Files
Extension to support large binary files in git repositoriesuses external storage (cloud)replaces actual files with a linkon checkout fetch the real file from the external storagesaves space in the repositorybut adds a dependency to an external service
httpsgit-lfsgithubcom
December 2019 8084
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
git-crypt - encrypt contents
Secrets (passwords application keys) should not be stored in(public) git repositoriesgit-crypt provides a way to store encrypted contents with GPG orwith simple shared keys
Create gitattributessecretfile filter=git-crypt diff=git-cryptkey filter=git-crypt diff=git-crypt
Use$ git-crypt init$ git-crypt add-gpg-user USER_ID$ git-crypt unlock
December 2019 8184
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
BFG Repo-Cleaner
Tool to clean up mistakes commited in a repository remove Huge binary files (executables images video)
either commited by mistakeor removed voluntarly by git rm but still occupying space fornothing in the repository
remove passwords or other kind of confidential data commitedby mistake
Warning this modifies the repository need to inform all usersbefore pushing
httpsrtyleygithubiobfg-repo-cleaner
December 2019 8284
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Agenda
1 Introduction2 Git concepts3 Individual developer4 Using branches5 Working in teams6 Git work flows7 Advanced branching8 Good Practices9 Other goodies10 Webography
December 2019 8384
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
Webography
httpsgit-scmcombookenv2The online Pro Git bookhttpswwwatlassiancomgittutorialshttplearngitbranchingjsorggraphical tutorial on branchesGit for computer scientists Tommi Virtanen june 2007Demystifying Git internals Pawan Rawal august 2016
December 2019 8484
- Introduction
- Git concepts
- Individual developer
- Using branches
- Working in teams
- Git work flows
- Advanced branching
- Good Practices
- Other goodies
- Webography
-
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