I just added the following note to the wiki and I want to repeat it here:
While it is possible to use a git mirror or other tools to use git for Mailman core and Postorius development, we DO NOT RECOMMEND USING GIT for GSoC. Merge requests need to happen on launchpad (that is the one way new code gets accepted into those projects), and previous GSoC students have found that the time required to make it all work is more than they anticipated. (We may one day switch to git, but it won't be happening this summer.)
Sorry! I know our official stance for regular contributors is "use whatever as long as you can submit a launchpad merge request" but for GSoC students, you're on a short timeline that's going to be busier at the end than the beginning and experience says it's much safer to learn launchpad and use it from the get-go than risk time-consuming problems later in the process.
Terri