development: revision controlcourses.cs.vt.edu/~cs2204/fall2007/notes/rcs-svn.pdfoverview of rcs and...

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Development: Revision Control

November 26, 2007

Class Meeting 14

* Notes adapted by Lenwood Heath from previous work by other members of the CS faculty at Virginia Tech

Lenwood Heath, Virginia Tech, Fall, 2004 2

Software Development Process

� Creation of source files� Text editors

� vi� emacs

� Revision (version) control systems� rcs / cvs

� svn

� Compilation and linking

� Running, testing, revising

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Development on a Server


Problems With Direct Access

� Every time a source file is edited, the old version is lost.

� The project as a whole can be in an inconsistent state while it is being edited.

� Developers may simultaneously edit the same source file, leading to multiple,

irreconcilable versions.

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How not to keep multiple versions of your files


What is revision control?

� Maintains versions of project files

� logged and archived

� enforces consistency

� Especially applicable when projects include:

� multiple files

� multiple developers

� maintenance (corrective and enhancing)

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Why do you need revision control?

� Software development is normally done in teams

� Multiple people may be responsible for code in a single file

� You may want to freeze a working version and create a new revision branch

� You may want to roll back development to a previous point in time


Example need for version control

� Acute problem: working on a website

� Can rarely test your changes locally for dynamic sites

� If you upload the wrong version of a file –poof, site is gone

� Google caching is your friend

� No substitute for real version control

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Team Project Development


Concurrent Versions Control

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Overview of RCS and SVN

� Maintains all committed versions of source files — SVN saves differences only

� Each version of each file has a unique revision number (e.g., 1.1, 1.2, 1.3.2.2)

� Supports merging two edits of the same file

� Can place metadata into source files

� Locking files for one user to edit


Comparison of RCS / CVS / SVN

� RCS – Designed for multiple users on one machine to work together on a project

� CVS – Central machine with multiple client machines working on a project

� SVN – Same as CVS except better version history / atomicity / consistent data handling / better branching

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Short plug: Use SVN where possible


Everyday SVN Commands

Get files from repositoryco

Check changes into repositoryci

Clears out local changes to filesrevert

Check for updates in repositoryup

Show status of working filesstatus

DescriptionCommand

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Everyday SVN Usage

co

edit/compile/testci

revert

status

up


SVN Example — checkout

$ svn co http://something.com/mine_projectmine_project

U mine_project/Makefile

U mine_project/mine1.c

$ cd mine_project/

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SVN Example — commit

$ vi Makefile

$ svn ci Makefile

Sending Makefile

Transmitting file data .

Committed revision 788.


SVN Example — status

[anray2@console amadeus]$ svn status

? X2.fab.tmp

! .

M X2.fab

A test.cpp

M expDSO/loadWorld.C

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Branching and merging

� What happens when need to take a stable codebase and go in two different directions with it?

� Two different engines / feature sets

� What happens when you want to make the changes the official code?


SVN branching

$ svn copy trunk branches/my-calc-branch $ svn status A + branches/my-calc-branch

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Checking out the newly created branch

$ svn checkout http://svn.example.com/repos/calc/branches/my-calc-branch

A my-calc-branch/Makefile

A my-calc-branch/integer.c

A my-calc-branch/button.c

Checked out revision 341.

-Can use svn switch also, but not recommended


Time progression of codebase

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Merging

$ svn merge -r 343:344 http://svn.example.com/repos/calc/trunk

$svn status

U integer.c

$svn ci


The ePaper trail

$ svn log -r 5:19 # shows logs 5 through 19 in chronological order

$ svn log -r 19:5 # shows logs 5 through 19 in reverse order

$ svn log -r 8 # shows log for revision 8

$ svn log foo.c

$ svn log http://foo.com/svn/trunk/code/foo.c

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Investigating old versions

� Can diff between revisions

svn diff –r 2:3 yourFile.c

� Can checkout old revisions, simply add a –r X to checkout revision X

svn co –r 100 http://svn.google.com


Putting SVN info in your programs

� $Date – the last time a file was changed

� $Revision – the last known revision for a file

� $Author – Who last changed the file

� $HeadURL – Where the repository came from

� $Id – Combination of date / revision / author

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Locking files

� svn lock filename

� Owner of locked file can update

� svn unlock filename

� Normal operations for the file

� Possible to break locks with admin programs if needed

� svn info filename will give you information on the lock


Other SVN Commands

Initialize a new SVN repositorycreate

Diff of working and repository filesdiff

Import files into repositoryimport

Remove file from repositoryrm

Add files to repositoryadd

DescriptionCommand

http://svnbook.red-bean.com/en/1.4/index.html

Details in this week's lab assignment

development: revision controlcourses.cs.vt.edu/~cs2204/fall2007/notes/rcs-svn.pdfoverview of rcs and...

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