Use the branch marker metadata as project filter

[lu-zero]

Some projects such as nginx use a single mailing list to track patches from multiple branches, they use mercurial so figuring out the branch is just a matter of parsing some #-comments in the patch comment.

git doesn't seem to have an immediate way to figure it out though, commonly some [marker] is used.

Open questions:

• Do we want to consider them separate projects and change just the parser
• Do we want to have the concept of subproject/branch as an ORM object and change the UI accordingly?

I'd start simple and consider each branch a stand-alone project.

[lu-zero]

@thresheek if you could provide a sample file and more insight would be great =)