Version control with CVS

1
Version control with CVS

• Apr. 16. 2005
• Joonmyung Kang
• eliot_at_postech.ac.kr
• DPNM Lab., Dept. of CSE, POSTECH

2
Presentation Outline

• Introduction
• Version Control Basics
• CVS
• Usage
• Demo

3
Version Control Basics

• copy of the source code kept in a repository
• repository records the history of code
• developers keep a local copy of their code
• developers can update their local copy to get
  changes others committed to the repository
• commit changes to the repository

4
Source Code Management

• The Problem you and a couple partners are
  working on a project. How do you handle the
  source code?
• The hard way you designate a guy to maintain the
  golden copy. As you finish code you give it to
  him, and he places it in a directory.
• Forces a guy to do this manually
• What if two people are working on the same file?
• What if you want to go back to an older version
  of a file?
• What if you want to maintain multiple forks of
  the program?

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Source Code Management

• These are the problems source code management
  intended to solve. Effectively it is a database
  for source code that eases the problems of
• Multiple people in many places working on the
  same code
• Retrieving old versions of files
• Keeping logs about what changed in a file
• Integrating changed code
• Generating release builds

6
The Concept
Repository
Checkout
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CVS

• manages changes on a per file basis
• log messages for each change
• remote repository access
• tagging a set of files for later access
• invoked as cvs from the command line
• most operations are not atomic
• never Ctrl-C cvs because it will leave your
  repository in an inconsistent state

8
Basic Tasks

• administrative setup
• getting a working copy
• committing and understanding changes
• adding a file
• removing a file
• updating to the latest code

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What You Can Do

• You can save every version of every file.
• Storing only the differences between versions
• When bugs creep in, you can retrieve old versions
  and see differences
• CVS merges the different work of each developer

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How to use CVS

• Repository setup
• Creating a directory tree
• Getting the working copy
• Committing changes

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CVS Environment Variables

• CVSROOT tells CVS the location of your repository
• CVS_RSH tells CVS how to connect to remote
  repositories
• you want to use ssh
• CVSEDITOR the program CVS invokes for editing
  commit messages
• CVS will use EDITOR if CVSEDITOR is not defined
• defaults to vi if neither defined

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Repository Setup

• .cshrc or .tcshrc (C shell)
• setenv CVSROOT pserveryourid_at_fraser.postech.ac.k
  r/home/cvs
• .bashrc (bash shell)
• Export CVSROOTpserveryourid_at_fraser.postech.ac.k
  r/home/cvs

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Creating a Directory Tree

• cd wdir
• cvs import m Message rdir vtag rtag
• wdir working directory
• rdir remote directory
• vtag vendor tag
• rtag release tag
• cvs import m Message Project park D100

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Getting the Working Copy

• cd ..
• mv wdir wdir.orig
• cvs checkout rdir
• mv Project Project.orig
• cvs checkout Project

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Committing Changes

• cvs diff main.c
• cvs commit m Message main.c

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Getting the Working Copy with Date

• cvs checkout D date_spec Project
• Date_spec a date description
• cvs checkout D 2004-09-01 Project

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Update Codes

• M file modified in your local copy
• U file brought up to date with repository
• P (same as U but happens more quickly)
• ? file is in your local copy but not in the
  repository
• C a conflict was detected between your local
  copy and the repository copy
• A file is scheduled to be added to the repository
• R file is scheduled to be removed from the
  repository

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Conflicts on Update

• your partners may have made changes that conflict
  with your changes
• known as a conflict
• C code on update
• edit the file to resolve the conflict
• commit only after you have resolved the conflict

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Others

• Adding new files
• Removing files
• Getting a working copy with date

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Adding Files and Directories

• to schedule a file in a directory already in the
  repository to be added
• cvs add file
• you must commit the file before it is added
• to add a directory inside a directory already in
  the repository
• cvs add dir
• there is no need to commit the directory because
  cvs doesnt really understand directories

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Removing a File

• files are not removed from the repository until
  you commit them.
• to remove a file from the repository and then
  from cvs
• rm file
• cvs remove file

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Removing a Directory

• cvs doesnt really understand directories, and
  thus has special behavior that works most of the
  time it prunes empty directories
• remove all the files in the directory and from
  cvs
• cd dir
• rm file1 file2
• cvs rm file1 file2
• make this easier with some shell magic
• rm file1 file2
• cvs !!

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Tagging the Current State

• you can mark the current state of your repository
  with a tag
• cvs tag tag-name
• to checkout a tagged release
• cvs checkout -r tag-name
• this sets a stick tag which will stay with your
  file until you unset it with
• cvs update -A

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Viewing Changes

• to view the difference between your current file
  and the latest file in the repository
• cvs diff file
• for differences between your file and a some
  previous version X.Y
• cvs diff -r X.Y file
• to view the commit messages for a file
• cvs log file

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Renaming a File

• to rename a file
• mv old new
• cvs remove old
• cvs add new
• cvs commit old new
• note that you loose a files revision history
  when you move it

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Renaming Directories

• mkdir newdir
• cvs add newdir
• mv olddir/ newdir
• cd olddir
• cvs remove file1 file2
• cd ../newdir
• cvs add file1 file2
• cvs commit
• cvs update -P

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Reverting Changes

• to revert a file in your local copy (based on
  version X.Y) to version W.Z in the repository
• cvs update -j X.Y -j W.Z file
• order matters
• directory and file renames cannot be reverted

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Adding Binary Files

• cvs expands the magic keywords like Id
• bad for binary files
• to add a binary file to cvs use
• cvs add -kb binary-file
• -kb tells cvs that the file is a binary file
• this is a sticky option

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Branching
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Keyword expansion

• Author
• Author eliot
• Date
• Date 2005/03/21 143232
• Id
• Id hello.c,v 1.1 2005/03/21 143232 eliot Exp
• Revison
• Revision 1.1
• Source
• Source /home/cvs/hello_world/hello.c,v
• Log
• Log hello.c,v Revision 1.2 2005/03/21
  143532 eliotlog messageRevision 1.1
  2005/03/21 143232 eliotThis is the first log
  messages

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The Future of Version Control

• bitkeeper http//www.bitkeeper.com
• subversion http//subversion.tigris.org
• arch http//arch.quackerhead.com/lord
• opencm http//www.opencm.org

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Conclusion

• Do not trust CVS
• CVS is not Backup system
• DPNM CVS
• http//dpnm.postech.ac.kr/cvs/
• DPNM homepage -gt Links -gt DPNM CVS Homepage

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Demo