First pass at a great workflow RFC to rule them all.

I'm much more concerned that we wind up avoiding tight integration with Git because we can't be fair to all VCS's and then have shitty Git support.  We need good Git support.  Absolute requirement.  We should write the code so we're not tightly coupled to Git.  Extending it to Hg or SVN or whatever should definitely be a stretch goal, though, and driven by customer demand and/or customer pull requests.