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Archiving your work with CVS. Jon Arrowood 2001-Nov-16. Overview. Version control What is it? Basic concepts Why should I use it? One particular method: “Concurrent Versions System”, or CVS Setting up a new project Manipulating a project Where to go for further help.

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Archiving your work with cvs l.jpg

Archiving your workwith CVS

Jon Arrowood 2001-Nov-16


Overview l.jpg
Overview

  • Version control

    • What is it?

    • Basic concepts

    • Why should I use it?

  • One particular method: “Concurrent Versions System”, or CVS

    • Setting up a new project

    • Manipulating a project

    • Where to go for further help


Version control what is it l.jpg
Version Control -- What is it?

  • An organized method of keeping track of the history of a set of files

  • The idea:

    • A set of files is checked out of the main repository to a directory, some are modified, then checked back in

    • Sets of files can be tagged with release names for an easy way to get groups of files (for example, “Release 2.0”).

    • Old versions of files can be retrieved at any time

    • Different versions can exist on different branches


Version control basic concepts l.jpg
Version Control -- Basic Concepts

The basic concepts are:

  • checking in revisions

  • tagging releases

  • branching releases

  • merging from branch to branch


Version control checking in revisions l.jpg

x.cpp

y.cpp

z.cpp

Ver. 1

Ver. 1

Ver. 1

Version Control - Checking in Revisions

  • For example, a repository begins with three files: x.cpp, y.cpp, z.cpp.

  • The three files are checked out.

  • After changes, z.cpp is updated, followed by x.cpp, then z.cpp again.

Ver. 2

Ver. 2

Ver. 3


Version control tagging releases l.jpg

x.cpp

y.cpp

z.cpp

Ver. 1

Ver. 1

Ver. 1

Ver. 2

Ver. 2

Ver. 2

Ver. 3

Ver. 3

REL_2_0

Version Control -- Tagging Releases

  • Take the repository we were just using.

  • Tag the latest versions as “Rel_2_0”

  • Further changes can be made at will

  • We can easily go back to REL_2_0 at any time


Version control branching merging l.jpg

rel_2_0

pre_rel_3_0

rel_2_1

rel_2_1

Version Control -- Branching/Merging

  • You’ve finished Release 2.0, and are working on pre-3.0

  • You find a bug in 2.0 that needs fixing now

  • Create a new branch, tag as Release 2.1

  • If required, merge changes into 3.0 track

  • Note that the boxes above refer to sets of tagged files, not individual files


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Version Control -- Various concepts

  • Version control is not just for C/C++ code!

    • Great for LaTeX

    • Matlab files

    • etc.

  • Files are saved as a base file, and diffs to give other versions

    • saves lots disk space

    • binary files must be checked in differently than text files

  • Watch out for End-Of-Lines if mixing Win32 & Unix

    • Lines end w/ “\r\n” in Win32 text files, but just “\n” in Unix

    • Refer to manuals on how your specific software handles this.


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Version Control -- Software Choices

Many different Version Control systems exist

All have basically the same functionality

  • Concurrent Versions Systems (CVS)

    • Available for any conceivable platform

    • Freely available

    • Mediocre GUI available (WinCVS)

  • Microsoft Visual SourceSafe (VSS)

    • Win32 only

    • Easy to use GUI

  • Perforce

    • Similar to VSS, but cross platform

    • Expensive (free, however, if <= 2 developers)

  • RCS

    • Old Unix software, replaced by CVS


Version control why use it 1 l.jpg
Version Control -- Why use it? #1

Excellent when project has > 1 person

  • Easy to merge in changes from an external group

  • Everyone has access to latest version

  • Easy to ensure that latest version works

    • can use automated tool (such as “tinderbox”) to verify that each version works, if you’ve written testing tools.

  • Automated notification to other developers when files are updated

  • Even if you’re the only user, you can have multiple simultaneous copies to work on


Version control why use it 2 l.jpg
Version Control -- Why use it? #2

Makes backups very easy

  • Repository is in a single location

  • Backups as easy as TGZ’ing or ZIP’ing one directory

  • Easily moved to a new machine

    caveat: I have no idea if this is true with VSS, but probably?


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Version Control -- Why use it? #3

Great way to keep track of small tests

  • When trying something new in your research, you can branch for new ideas

  • Easy to return months later to a particular test

  • Test code can later be merged into your main code in a straightforward manner

  • No more naming-work-directories-with-today’s-date


One particular piece of software cvs l.jpg
One particular piece of software: CVS

CVS is particularly nice:

  • freely available

  • already installed on systems in CSIP

  • ported to almost every platform

  • has a Win32/Unix/Mac GUI

  • very popular


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Using CVS: Initializing a repository

  • Requires an environment variable, giving the location of the repository:

    [jon@yamwb]$ export CVSROOT=$HOME/cvsroot

  • Initializing repository is then done by:

    [jon@yamwb]$ cvs init

  • Running init on an already existing repository won’t harm it


Using cvs starting a new project l.jpg
Using CVS: Starting a new project

  • Begin with a directory of existing code (say it’s called “project1”)

    [jon@yamwb]$ ls

    project1/

    [jon@yamwb]$ cd project1

    [jon@yamwb]$ cvs import project1 jon start

    <an editor will pop up forcing you to add comments>

    [jon@yamwb]$ cd ..

    [jon@yamwb]$ mv project1 project1-to-be-deleted

    [jon@yamwb]$ cvs checkout project1

    [jon@yamwb]$ ls

    project1/ project1-to-be-deleted/

  • The new “project1” directory is now ready for use with CVS


Using cvs l.jpg
Using CVS:

  • Always use “cvs checkout” before working on the files (of course, save the orig directory until you’re sure you’re using CVS correctly!)

  • Inside of the new project1 directory, you’ll find a subdirectory named “CVS”.

    [jon@yamwb]$ ls project1-to-be-deleted

    file1 file2 file3

    [jon@yamwb]$ ls project1

    CVS/ file1 file2 file3

    [jon@yamwb]$

  • This directory contains the history info for the local files, so comparisons can be made to the repository later on


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Using CVS: Committing file revisions

  • Checkout a project, change some files

  • When you’ve made a significant change that you’d like saved simply run

    [jon@yamwb]$ cvs commit

    or

    [jon@yamwb]$ cvs commit file1 file2

  • Default action is to check in any locally modified files in the current, or lower, directories.


Using cvs adding files to a project l.jpg
Using CVS: Adding files to a project

  • Go inside a project directory already under CVS control (ie, it has a “CVS/” subdirectory)

  • Create some new_file

    [jon@yamwb]$ cd project1

    [jon@yamwb]$ ls

    CVS/ file1 file2 file3

    [jon@yamwb]$ echo “foo” > bar

    [jon@yamwb]$ cvs add bar

    [jon@yamwb]$ cvs commit bar

    <an editor will pop up forcing you to add comments>

  • require “-kb” qualifier if files were binary:

    cvs add -kb binary_file


Using cvs tagging a release l.jpg
Using CVS: Tagging a release

  • To tag a release

    [jon@yamwb]$ cd project1

    [jon@yamwb]$ cvs tag REL_1_0

    Note: only the checked-in files are tagged, if you’ve locally modified files, you must ‘commit’ them first.

  • To retrieve this version of the code, at any time

    [jon@yamwb]$ cvs checkout -r REL_1_0 project1

    [jon@yamwb]$ ls

    project1/

    Note that you can have different versions of the same project checked out in different places.


Using cvs branching merging l.jpg
Using CVS: Branching/Merging

  • Beyond the scope of this talk, look in the extensive online docs at www.cvshome.org

  • One hint: mistakes can be made when branching or merging. Always backup your CVSROOT repository before major operations.


Using cvs utilities l.jpg
Using CVS: Utilities

  • cvs status -v some_file

    • lists all tags associated with a file

  • cvs diff some_file

    • generates the diff between your local version of some_file and the current repository version

  • cvs diff -r REL_TAG some_file

    • generates the diff between your local version and an arbitrary repository version


Version control review l.jpg
Version Control -- Review

The basic concepts are:

  • initializing a repository

  • importing an initial directory

  • changing files, then committing those changes

  • adding new files, then committing them

  • tagging releases

  • creating branches

  • merging from branch to branch


Using cvs various l.jpg
Using CVS: Various

  • CVS works over networks, so you can keep your cvsroot at school, but checkout from home.

  • Secure shell easily used: export CVS_RSH=ssh

  • Files/directories are never completely removed. If they existed once, you might always ask for them back.


Resources for cvs l.jpg
Resources for CVS

  • www.cvshome.org

    • for generic info on CVS

  • www.wincvs.org

    • for Win32/Linux/Mac GUIs for CVS

  • webCVS (can’t find a site for it right now…)

    • a CGI script that lets you browse your repository with Netscape. Only for browsing -- you can’t change anything