While looking at this question I realised that I'm not too clued up on how Geth's different branches relate to each other.

For example, the PPA pushes out v1.5.0-unstable, which doesn't contain the changes made for the hard-fork, which went into 1.4.10. (I'm thinking specifically of this commit, which introduced the --oppose-dao-fork and --support-dao-fork flags.)

What are the rebase/collapse schedules relating to the different branches (I'm thinking master, develop and versioned branches), and more specifically, how do the PPA packages pick up the changes from these branches?

I'm hoping for a lovely branch diagram in the answer, but I'll settle for anything you've got...