Why CVS is Your Friend

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Why CVS is Your Friend

• Amandeep Jawa
• deep_at_worker-bee.com
• Worker Bee Software

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Why You Should Care

• CVS can make your job easier
• CVS saves YOUR time and effort
• CVS will save your butt (trust me)
• CVS is mandatory -)

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Agenda

• Version Control Overview
• CVS Concepts
• Basic CVS Work Flow
• Most Common Commands
• Additional Commands
• Commands you might not use
• Additional CVS Features
• Tips Warnings
• References
• Summary

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What is Version Control Good For?

• Maintaining project/file history - so you dont
  have to worry about it.
• Managing collaboration on files and projects - so
  multiple developers can work on the same set of
  files
• Managing releases - so you know what files are in
  what version.

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CVS Concepts

• CVS becomes easy to use once you understand the
  concepts behind it
• The Repository The Magic Place That Holds All
  Versions of Everything
• Your Working Copy(ies) The place(s) where you
  get to do whatever you want.
• The CVS program manages moving files between the
  two.

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Basic CVS Work Flow

• Get a working copy
• Make changes in your copy
• Test them locally
• Integrate them with any changes made to the
  Repository
• Commit them back to the Repository
• Repeat these steps until a release is ready
• Tag the release
• Start making changes again for next release

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CVS Command Structure (Commandline)

• cvs global options command command options
  files
• There a few global options - most useful are
• -n dont actually DO the next command - just
  show what you would do. Really useful for update
• -H display help on the given command
• -q or -Q quiet or VERY quiet
• Each command has its own set of options
• By default most commands operate recursively - be
  careful

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Common Commands Overview

• Checkout Makes your working copy
• Update Updates your working copy with the latest
  files from the Repository
• Commit Commits the latest changes from your
  working copy to the Repository
• Log Look at the history of a file(s)
• Diff Compare two versions of a file
• Tag Label a version (also used for branching)

Remember that most commands have MANY options
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Checkout

• Makes your working copy from the Repository
• cvs checkout ltproject_namegt
• Run this command from the parent directory of
  your working copy
• Useful command options include
• -r to get a specific revision or symbolic tag
• E.g cvs checkout -r 1.3 my_project
• -D to get a specific date
• E.g cvs checkout -D 17 May 2001 my_project
• E.g cvs checkout -D 2 weeks ago my_project

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Update

• Updates your working copy with the latest files
  from the Repository
• cvs update ltfile/directory namegt
• Merges changes from the Repository into your code
  unless you tell it not to
• Reports the state of the files in your working
  copy
• Useful global options include -n -q

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Update (continued)

• Useful command options include
• -A Remove all sticky tags so that the latest
  version can be retrieved
• -d Creates updates any new project directories
  created
• -j Can be used to retrieve a specific file/folder
  version (will set a sticky tag)
• -p Prunes empty directories
• We recommend always using -dp

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Update (continued 2)

• Update reports the state of each file with a line
  for every file such as X somefile.java where X
  may be
• A File added but not committed
• C Conflict detected - working copy must be
  hand-merged
• M Modified - you have modified your working copy
  it has not been committed to the Repository yet
• R File removed but not committed
• U File was updated from Repository
• ? File is not in Repository is unknown to CVS

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Update (continued 3)

• If a conflict occurs, there is nothing to panic
  about - conflicts are usually easy to fix.
• A conflict area will be marked in the working
  copy like this
• ltltltltltltlt file name
• ltthe uncommitted changes in your working copygt
• ltchanges committed to the Repository since you
  last updatedgt
• gtgtgtgtgtgtgt 1.7
• To resolve the conflict, simply edit the file
  replace the conflict area with whatever SHOULD be
  there. You may need to discuss the area with the
  other developer.

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Commit

• Commits the latest changes from your working copy
  to the Repository
• cvs commit ltfilenamegt
• After committing, you will be prompted for a log
  comment.
• You must enter a log comment when you commit
• Useful command options include
• -m to enter a log comment without being prompted

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Log

• Look at the history of a file(s)
• cvs log ltfile or directory namegt

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Diff

• Compare two versions of a file
• If one file is specified, it is compared against
  the repository, a tagged version, a revision, or
  a dated version
• If 2 files are specified, they are compared. The
  files can be specified by revision number, tag,
  or date

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Diff (continued)

• A difference area will be marked in the working
  copy like this
• lt ltthe lines from the 1st file (or the
  repositorygt
• ---
• gt ltthe lines from the 2nd file (or the current
  versiongt
• Various useful options exist including -c which
  shows lines of context around each area of
  difference

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Tag

• Label a version or create a branch
• cvs tag lttag_namegt
• Tag names must start with a letter can only
  contain numbers, letters, -, _
• Useful command options
• -d removes the tag
• -F moves the tag to the given revision or current
  version
• -b is used to create a branch tag - which is how
  a branch is started.

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Additional Commands Overview

• Add Adds a new file or folder to the Repository
  (be careful with binary files)
• Remove removes a file from the Repository
• Branch Allows you to make changes to an old
  version of the project later integrate this
  into the latest version
• Status Gives you detailed information about a
  file

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Add

• Adds a new file or folder to the Repository
• cvs add ltfile or foldergt
• Adding a folder is simple - but note it does not
  add the contents
• Adding files is a 2 step process
• If the file is a binary file, make sure you add
  it with the -kb option

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Remove

• Removes a file or folder from the Repository
• cvs remove ltfile or foldergt
• After removing a folder you should prune it
• When removing a file you must remove it from the
  file system first
• Removing files is a 2 step process

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Branch

• Allows you to make changes to an old version of
  the code later integrate this into the latest
  version

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Branch (Continued)

• To create a branch
• Make a new directory you want to use for the
  branch
• Cd to the new directorys parent directory
• Get the version you want to branch from
• cvs checkout -d ltnew_directorygt -r ltoriginal_taggt
  ltproject_namegt
• Cd into the new project directory
• Make a branch
• cvs tag -b ltbranch_tag_namegt
• Prepare the branch for editing
• cvs update -r ltbranch_tag_namegt

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Branch (Continued 2)

• To merge a branch back into the main development
  tree
• cvs update -j ltbranch_tag_namegt
• If you have any conflicts, deal with them as
  usual.

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Status

• Gives you detailed information about a file
• cvs status ltfile namegt
• Tells you about any sticky tags that are set

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Commands you might not use

• Import For putting an entire set of files into
  the Repository - used to start a project
• Export Create a working copy with NO CVS
  information - good for src dumps
• Help Prints out command summaries
• Admin Allows you to modify various things such
  as log messages the files keyword substitution
  mode

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Additional CVS Features

• cvsrc lets you set default command options for
  yourself
• cvswrappers set default options for specific
  file types
• cvsignore sets file types to just ignore
• loginfo, taginfo, etc set requirements for
  logging tagging format etc.
• Keyword expansion
• Watches, Emails, Locking etc.
• Annotation

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Tips Warnings

• Turn off keyword expansion for binary files
• Sticky Tags are set whenever you get a file by
  revision, tag or date
• Checkout from top
• Add commit
• -dp for latest directories

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More Tips Warnings

• Date can be specified in English like yesterday
  or 2 weeks ago
• Recursive

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References

• Version Management with CVS by Per Cederqvist,
  www.cvshome.org
• CVS Pocket Reference Gregor Purdy, published by
  OReilly
• Open Source Development with CVS Fogel Bar,
  published by Coriolis cvsbook.red-bean.com
  (Book/Partially Online)

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Summary

• CVS makes your job easier by maintaining your
  files history making it possible to have
  multiple developers working on the same set of
  files without bloodshed
• CVS moves files between the Repository your
  working copy
• Help Prints out command summaries