The Concurrent Versioning System (CVS) is a nifty package that allows you to simultaneously edit and manage source code and other files. Almost every open source software project uses CVS.
You can anonymously access Squid's CVS files (read-only) to keep your source code up to date. The nice thing about CVS is that you can easily retrieve only the changes (diffs) of your current version. Thus, it is easy to see what has changed recently. Applying the changes to your current files efficiently synchronizes your source code with the official version.
CVS uses a tree-like indexing system. The trunk of the tree is called the head branch. For Squid's repository, this is where all new changes and features are placed. The head branch usually contains experimental and, possibly unstable, code. The stable code is typically found on other branches.
To effectively use Squid's anonymous CVS server, you first need to understand how different versions and branches are tagged. For example, the Version 2.5 branch is named SQUID_2_5. Particular releases, which represent a snapshot in time, have longer names, such as SQUID_2_5_STABLE4. To get exactly Squid Version 2.5.STABLE4, use the SQUID_2_5_STABLE4 tag; to get the latest code on the 2.5 branch, use SQUID_2_5.
To use the Squid anonymous CVS server, you first need to set the CVSROOT environment variable:
csh% setenv CVSROOT :pserver:firstname.lastname@example.org:/squid
Or, for Bourne shell users:
sh$ CVSROOT=:pserver:email@example.com:/squid sh$ export CVSROOT
You then log in to the server:
% cvs login (Logging in to firstname.lastname@example.org) CVS password:
At the prompt, enter anoncvs for the password. Now you can check out the source tree with this command:
% cvs checkout -r SQUID_2_5 -d squid-2.5 squid
The -r option specifies the revision tag to retrieve. Omitting the -r option gets you the head branch. The -d option changes the top-level directory name in which files are placed. If you omit the -d option, the top-level directory is the same as the module name. The final command-line argument (squid) is the name of the module to check out.
Once you have the Squid source tree checked out, you can run the cvs update command to update your files and synchronize with the master repository. Additional interesting commands are cvs diff, cvs log, and cvs annotate.
To learn more about CVS, visit http://www.cvshome.org/.