dist-git proof of concept phase 2 ready for testing

[Kevin Kofler]

Jesse Keating wrote:
> Nobody should be able to create any branches that do not start with
> "private-".

I really don't see the point of this, why can't we just allow any branch 
name that isn't a reserved name (master or F-[0-9]+)?

> We'll make sure that the buildsystem will not allow any official
> (non-scratch) builds to happen from a private-* branch.

And as I wrote before, I don't like this at all, it's a regression from our 
current workflow and it defeats the point of the much-touted easy branching 
with git.

        Kevin Kofler