The current Squid development model makes extensive use of branches, where each developer or task is given a unique branch containing specific feature changes.
To become a developer please follow the guidelines at http://wiki.squid-cache.org/DeveloperResources. The instructions there cover everything from what tools you need, developer contacts, coding styles and how best to access the code.
Developers are assumed to know and follow these simple rules (separate page)
And to use these tools (separate page) to maintain their work in the CVS repository.
This service is built around the service provided by SourceForge.