[RFC] Porting builtin/branch.c to use the printing options of ref-filter.{c,h}

I'm working on porting over the printing options of ref-filter to `git branch -l`. This is a follow up to http://article.gmane.org/gmane.comp.version-control.git/276377

Theres a slight issue with this which I'd like to discuss about.

When we use `-a` option in `git branch -l` It lists local branches and remotes with each having a different output format. This with reference to ref-filter would mean either

1. Change format in between local and remote refs
2. Have a format like %(if)...local check....%(then)....local branch
format....%(else)....remote format %(end).

I prefer the latter, but that might lead to a large format. Any suggestions?