Concurrent Versions System
• Overview of CVS architecture.
• Repository structure.
• Basic development tasks in WinCvs.
• Branching and merging.
• Other CVS interfaces
• CVS internals
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
CVS Features
• Concurrent access by multiple developers
• Multiple development lines in a single repository
• Grouping sources into modules
• Symbolic source tagging
• Diffs between versions
• Configurable logging support
• Binary files support
• Repository event triggers
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Client-server architecture
• separate server (UNIX or NT)
• no shared filesystems
• a server process per connection
ewacvs
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
The CVS Repository
ewacvs:/data1/cvsroot
CVSROOT
shr project1 project2 project3 devkits
ar
cgi doc install reports
cgipr
unix
nt
• Resides on a server
• No working files inside the repository
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
util
web
esapps
forms
CVS Usage Model
Checkout, Commit, Update
• Checkout
Makes private copy in working directory
Can check out anywhere
Check out multiple copies, multiple versions
• Commit
Commit changes to the repository when finished
Working copies must be up to date with repository
• Update
Brings working copy up to date with repository
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Concurrent checkout
Checkout does not lock
the files in repository
Master Repository
foo.c
Karen
Michael
Working
Copy
V1.7
checkin
V1.8 or 1.9
Brigid
Chris
Working
Copy
V1.1
X
Working
Copy
V1.2
X
checkin prohibited
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Working
Copy
V1.7
checkin
Patrick
Working
Copy
V1.2.2.1
checkin
V1.2.2.2
V1.8 or 1.9
CVS and the Development Cycle
1. Check out source files in working directory.
2. Edit source files.
3. Unit test your code.
4. Update working files to merge in changes from
other developers (if necessary).
5. Test again if the sources were merged on step 4.
6. Commit changes.
7. Repeat from step 2 until you have a new release.
8. Tag the release.
9. Submit the module name and release tag for
integration build.
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Ideal development with CVS
development
checkout
checkin
update
Developer A
repository
Developer B
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Real development with CVS
checkin
conflict
checkin
update
resolution
Developer A
repository
Developer B
X
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
conflict
WinCVS on your desktop
•
•
•
•
•
•
•
•
Configuration
Main screen
Checking out the sources
Viewing source history
Diff
Commit
Update
Tag
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
WinCVS: Configuration
Your UNIX login
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
WinCvs: Main screen
file view
modules
status view
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Checking out the sources
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Source history & diff
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Commit, Update & Tag
update
commit
tag
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
When to commit
• Commit to mark a working state that you
might want to return to later.
• Commit related files in a single operation.
Use a common log message for all the files.
• Commit to backup your sources.
• Commit from an office desktop to be able to
access the files from home much faster than
through filesystem sharing.
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Working on branches
patch
cvs tag -b rel_1_fix
1.2.2.1
1.1
1.2
1.2.2.2
1.3
release_1
1.4
release_2
cvs up -r rel_1_fix
cvs tag release_1
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
cvs tag release_2
Branch if you need ...
• to create sustaining (patch) releases
• to have multiple development lines from a
single repository
• to do experimental development to merge
later or forget about it
• to keep temporary state of development
without affecting builds
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Common CVS commands
cvs [cvs-options] command [cmd-options] [files]
cvs checkout Check out source for editing.
cvs add
Add new file/directory to repository.
cvs remove
Remove an entry from the repository.
cvs status
Show status of checked out files.
cvs log
Show revision history for files.
cvs diff
Compare working files to version in repository
or versions inside the repository.
cvs update
Bring working files into sync with repository.
cvs commit
check files into the repository
cvs tag
Label the sources.
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Other CVS clients
CVSweb
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Diff
Directory
between
listing
2 versions of the file
Other CVS clients
jCVS
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Diff
Directory
betweenlisting
2 versions of the file
CVS online
• Official CVS site: http://www.cyclic.com
• CVS Bubbles: http://www.loria.fr/~molli/cvs-index.html
• CVS for Web development: http://durak.org:81/cvswebsites
• WinCvs: http://www.wincvs.org
• jCVS: http://www.jcvs.org/
• Netscape’s Mozilla under CVS:
http://cvs-mirror.mozilla.org/webtools/tindertest/showbuilds.cgi?tree=SeaMonkey
• FreeBSD CVS repository:
http://www.freebsd.org/support.html#cvs
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
CVS Internals
• Server is started via inetd (UNIX) with a process per
connection
• Client-server protocol has embedded compression
• Update sends file’s diff across the line, not the whole
file (when possible)
• UNIX authentication, optional CVS specific
passwords/groups, Kerberos and SSH support
• CVS does not have to run as root
• SCCI and OLE support are in development
• Event triggers are implemented via external
programs (Perl, sh, C, anything else)
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Reserved Checkouts and CVS
Exclusive file locking prevents parallel development
and is not recommended for plain text files
• advisory locks: implemented via cvs edit
and cvs watch. Get notification when
someone edits or checks in the file.
• all-o-nothing advisory locks: cvs edit does
not succeed if files are already edited by
someone else. Implemented using a patch to
cvs edit
• exclusive locks (RCS style): implemented
via cvs admin. You cannot commit unless
you’ve locked the file. One lock per file per
branch.
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Advisory locks
Developer A
email alert
CVS server
Editors:
Developer A
Developer B
Warren Jones, Fluke Co., Eugene Kramer, Remedy Co. Introduction to CVS 1999
Developer B