Git vs cvs ece2011

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April 12, 2023 Copyright © 2011 compeople AG, Made available under the Eclipse Public License v 1.0

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Christian Campo

EclipseCon Europe 2011

Git from a different (CVS/SVN) perspective

Copyright © 2011 compeople AG, Made available under the Eclipse Public License v 1.0 2

Copyright © 2011 compeople AG, Made available under the Eclipse Public License v 1.0

Git vs CVS vs SVN

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Git

• commits like db transactions

• commits linked in a hierarchy

• commits contains for a collection of files

• decentral repo

CVS

• commits are unrelated file diffs

• central repo

SVN

• commits are file diffs

• commit file diffs can be linked with a common revision

• central repo


Git Promises/Claims

you get your own local repository

you can commit even offline (in an airplane)

branching is easy and no longer an unusual task but part of your everyday workflow and its so much easier with Git

you hated merging with CVS (SVN) ? you are going to love it with Git

Git is fast and easy

you cant run an open source project without Git

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Git promises from the CVS angle

you never wanted a local repository

you hate to fly and therefore never commit in an airplane

you hate branches and actually never create them yourself

you have a different definition of merge, if two people modify unrelated files thats NO MERGE.

Git is fast ! but not easy

successful open source only requires Git....seriously ?

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• you can only checkout a whole repo with all projects (modules)• you get the whole history of the last 1-5 years• and all branches• isnt Internet now officially everywhere ?• and even if you are offline, just write code for a change• your release engineer does that• so now you should create branches ? NO way• branches isnt that like a fork ?

• no javadoc• no unit tests• no clean code• no integration tests• JUST Git ??


Git is giving words/things a new meaning

commit does not mean everybody can see your code

merge happens even if you edit unrelated files

first commit THAN merge THAN possibly commit again ?? and then....the merge commit is empty ? (has no diff)

repository is not one central thing on the server but everyone has one

branches on client and server can have different names its ok if two repos dont carry the same branches/tags

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CVS Users Migration Steps

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Step 1: Resistance


CVS has a real Synchronize

Synchronize shows me the list of incoming and outgoing changes on file level

helps to not check in stuff that I dont intent to

often people check incoming changes on a detailed level helps to understand what other people changed refactor stuff that seems wrong check typos :-) improves the quality of the code update is done step by step like kind of a to-do-list

there is Synchronize in Git, but you can not incrementally update (because of the concept of Git)

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Things only CVS can do

you can tag projects independant as you go

you can tag single files later

selectivly update only some projects

NOT resolve conflicts when you update (i.e. a xx.launch file that you changed)

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CVS Usage is NOT problem free

If you branch you almost never merge (because its so hard)

it was always complicated to figure out what was changed for a certain changeset ?

A "changeset" are merely commits with the same message so it is easy to amend a commit :-)

did you ever tag before and after a commit to log the difference ? if you develop in HEAD and a version branch und later you have to copy

changesets from HEAD to the version branch

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More CVS crap

Refactoring (renaming a class) means loosing all your history

Renaming a package, project means loosing all history of all objects in that package/project

If you delete a project it does not get deleted at your collegues workspace committer unless you TELL him. (and he deletes it manually)

If you add a project your collegues wont find out until you TELL them.

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And you come to Git...

And people tell you....the easiest way to use Git is the command line

however the command line is way better than you expect

it was created to actually work with it on a daily base

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CVS User Migration Steps

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Step 2: Euphoria

„Git is CVS without its problems, I have“


Pitfalls in Git

you try to pull before you committed your changes

you push .... EVERYTHING (including all local branches)

you create a new project in the root of the Git Repository directory

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Pitfalls in Git II

Merge conflicts are a little more complicated CVS flags the conflict Git Pull actually puts a comment in the file (so that it doesnt compile)

Rebases can be scary (rerunning commits on a different branch and hoping that the commits also work there)

Merge conflicts in the middle of a rebase even more

You always have to update everything (no way to exclude a bundle or a file)

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More stuff...

CVS users moving to Git think that Git is the solution to everything they missed in CVS

yes moving content between files means that Git still can keep track of the history

try to rename a bundle (just for fun) and then look at the proposed commit (there is “git mv” though)

you hear that the Git repo of the Eclipse platform was corrupted by a single committer (Is Git the right move for me ?)

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CVS User Migration Steps

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Step 3: Realtity

Understanding what you can do


Where Git is better than CVS (the centerpiece)

commits changes collected together in one metaobject called commit put more effort in creating a good commit amend a commit if wrong, dont just add a second (like in CVS) make smaller commits commits should be a "unit-of-work" useful by itself

a good history is the key to using Git

only Git commits truely show which modifications where committed together

there is no commit in CVS !!! Its just writing a collection of diffs..

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Things only Git can do

Pick some commits from one branch into another (cherrypicking)

Revert commits

Merge branches (and that actually works :-) )

Rebase your local changes on top of the server master

Work on commits in the past Tag them Branch from them Sign them Reset your workspace to that time in history

If you manually undo the changes in a file it automagically shows the file as unmodified.

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Things only Git can do

develop multiple features in parallel without checking-into-the-server-repo

stash your current work, while you do something else and then come back to your work in progress

commit only parts of the changes in a file

freeze a state of your files before they are committed (staging area)

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Git is confusing at times

It uses names that CVS uses, but means something different commit, merge, repo

local tracking branches can have a strategy

git history can be confusing and complicated

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Summary

Dont treat Git as if it were CVS.

Getting from CVS to Git requires you to "re-wire" your brain get used to a new way of doing things adapt your way of doing things to retain your workflow as much as

possible

Symptoms are similar to learning any kind of new technology remember XML, Javascript, Objective-C, Modeling, XText, Tycho

Git opens the door for better collaboration and contribution from others

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And...one more thing....

...you can commit in an airplane


THANK YOU

Git vs cvs ece2011

Technology

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compeople ag

eclipse public license

git promisesclaims

git vs cvs vs svn git

merge commit

cvs svn

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