So, you want to help out with Bugzilla development! Great! Here's what you should do (most items have a link to more details):
1. Introduce yourself on the developers mailing list.
2. If you don't know what you'd like to work on, look at the list of bugs we've marked as being good for newcomers. If you already know what you want to work on, first check if a bug has already been filed for it, and then check that bug's priority.
3. Get in communication with the Bugzilla developers, and talk about what you want to do. This makes it easy for us to tell you "Oh, we're already working on that, you can help!" or "Oh, the best way to do that would be..."
4. Check out the latest Bugzilla code from git. You always want to work against the master branch of Bugzilla, not a released version, if you're writing patches that you want us to accept.
5. Write some code. Make sure that you follow the Developer's Guide. If you're new, you don't have to read the whole thing. Just read the General Guidelines, the Style section, and any other part that you think applies to the code that you're writing. Make sure that your patch is as simple and small as possible. And make sure that you license each file correctly.
6. Test your code. Make sure it works, and run ./runtests.pl in the Bugzilla directory. Also use the HTML validator to make sure your code generates valid HTML, if you modified any of Bugzilla's HTML.
7. Make a patch
8. Submit your patch in Bugzilla
10. Once your bug has passed review, the reviewer will ask for "approval". When approval is granted, you or the reviewer can push the patch to Git.
11. Push your patch, or get somebody else to push it for you.
Articles and Policies
These are various essays and guides that help with Bugzilla development.