parse_git_branch, still

I'm still working with the parse_git_branch script that goes against the plumbing instead of the porcelain to get it right (well, I haven't done any of the actual work). I'm beginning to think that it's better to use what I had before (I'll redo it in Ruby sometime, probably): if you compare using git status (inflexible) to writing  your own git status (crazy!), the former has some clear advantages: git status is a relatively complex program that works.