The Bugzilla Project uses the git Version Control System. You can see the contents of the Bugzilla git repository on Github.
Checking Code Out of git
The simplest way to get the latest Bugzilla development code is:
git clone https://github.com/bugzilla/bugzilla
That will clone the Bugzilla git repository into a directory called "bugzilla" and will check out the "master" branch.
If you want other branches, in the bugzilla directory simply checkout another branch:
cd bugzilla git checkout 4.2
That will switch the files in the working directory to latest commit on the 4.2 branch. Note that this doesn't necessarily correspond to the latest release in that series; additional patches may have been checked in since.
If you have checkin rights and plan to use them, remember to also execute:
git remote set-url --push origin firstname.lastname@example.org:bugzilla/bugzilla.git
Getting A Specific Release
Every time we release a version of Bugzilla, we tag the git repository so that the point in history that matches with that release can be explicitly checked out of the repository. For example, to check out Bugzilla 4.1.3, you would do:
git checkout release-4.1.3
That will switch the files in the working directory to the commit released as version 4.1.3.
You will usually get a warning here about being in a "detached HEAD" state; this is fine unless you'll be modifying the code in your installation, at which point you should create a local branch to preserve your change history.
To see a list of all the tags available do