Basics of Version Control Systems · What are VCS Software development perspective Version control systems (VCS) (or Source Conﬁguration Management (SCM) systems ) allow developers

Intro Basics VCS Cheat sheets

Basics of Version Control Systems

Lars Vilhuber1

1Cornell University, Economics Department,

August 20-22, 2018: Day 2

Vilhuber Basics of VCS


What are VCS

Software development perspectiveVersion control systems (VCS) (or Source ConfigurationManagement (SCM) systems ∗) allow developers or authors tokeep track of the history of their projects? source code. [source]

Generic viewDetailed mechanism to manage different versions (historical,parallel) of documents, files, programs, etc.


http://better-scm.shlomifish.org/


What are VCS

Software development perspectiveVersion control systems (VCS) (or Source ConfigurationManagement (SCM) systems ∗) allow developers or authors tokeep track of the history of their projects? source code. [source]

Generic viewDetailed mechanism to manage different versions (historical,parallel) of documents, files, programs, etc.


http://better-scm.shlomifish.org/


You already have it

Implicit uses

I Backup systems (Apple Time Machine, others)I Word processors (Undo feature, Track changes in Word,

finer-grained features in content management systems:Google Docs, Blog software, etc.)

I Versioning filesystemsI Paper books!



Modern Labor Economics: Theory and Public Policy



Modern Labor Economics: Theory and Public Policy



Principal idea

1 First edition

4 Second edition5 Start of work on a

Canadian edition6 Start of work on the next

US edition9 Third edition

10 First Canadian edition



Principal idea

1 First edition4 Second edition

5 Start of work on aCanadian edition

6 Start of work on the nextUS edition

9 Third edition10 First Canadian edition



Principal idea

1 First edition4 Second edition5 Start of work on a

Canadian edition

6 Start of work on the nextUS edition




Principal idea



US edition




Principal idea







Principal idea







File-system based versioning

The most common method... Also used in email versioning...

Remember this?01 01 readBLS.R

02 01 readCensus.R

02 02 prepareCensus.R

03 01 create analysis data.R

04 01 runOLS.sas

README.txt





What if I make changes?

01 01 readBLS.R

02 01 readCensus.R



04 01 runOLS.sas

README.txt

02 01 readCensus.R.bak

02 01 readCensus V2.R


02 01 readCensus V3-jma.R

02 01 readCensus V3-jma-rm.R






01 01 readBLS.R

02 01 readCensus.R



04 01 runOLS.sas

README.txt











01 01 readBLS.R

02 01 readCensus.R



04 01 runOLS.sas

README.txt











01 01 readBLS.R

02 01 readCensus.R



04 01 runOLS.sas

README.txt











01 01 readBLS.R

02 01 readCensus.R



04 01 runOLS.sas

README.txt











01 01 readBLS.R

02 01 readCensus.R



04 01 runOLS.sas

README.txt








Better way

Is there a better way?



History



Two major types of version-management

Centralized modelServer-client approach, editors check out a copy, modify it, andcheck it back in. Multiple editors:I File locking: only one person can check out any given fileI Version merging: discrepancies are handled upon checkin

Distributed modelThere is no central server (prescribed by software). Everyeditor has a full copy of all version, synchronisation occurs byexchanging patches.



Two major types of version-management

Centralized modelServer-client approach, editors check out a copy, modify it, andcheck it back in. Multiple editors:I File locking: only one person can check out any given fileI Version merging: discrepancies are handled upon checkin

Distributed modelThere is no central server (prescribed by software). Everyeditor has a full copy of all version, synchronisation occurs byexchanging patches.



Focus in this class

We will focus on Git:I Subversion (centralized) - still broadly in use, but no longer

supported at CornellI Git (decentralized) - Hautahi

Windows TortoiseGit (free)OSX installed (Xcode) upon first useLinux typically integrated

with various semi-specialized graphical versions (Githubclient, etc.)


http://tortoisegit.org/


THE reference for Git

git-scm.com/book/en/v2


https://git-scm.com/book/en/v2


Learning more

Numerous resources on the webI https://try.github.io/

I https://www.atlassian.com/git/tutorials


https://try.github.io/

https://www.atlassian.com/git/tutorials


Tracking history

What happened? And who did what?One of the key advantages of using version control systems is... to control versions.I Straightforward to view multiple versions of a file

(assuming proper usage)I Possibility to view who changed what (“blame” or

“annotate”)



Tracking using web interfaces: SVN












Tracking using web interfaces: git









VCS infrastructure

At CornellCornell Sourceforge (obsolete as of Sept 30, 2018)

ElsewhereI GitHub (Git, subversion, free for open-source and

academic users)I BitBucket (Git, no subversion, free for academic users)I Roll your own: no server required for Git on your PC


https://forge.cornell.edu/sf/sfmain/do/home

https://github.com/plans

http://bitbucket.org/


I Git command-line cheat sheetI Xcode cheat sheet (for Mac users)


Basics of Version Control Systems · What are VCS Software development perspective Version control systems (VCS) (or Source Conﬁguration Management (SCM) systems ) allow developers

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