(feature request) include local branch name

[oleg-codaio]

When using git spr update, branches get pushed up with names like spr/*****, along with associated pull requests.

However, the original local branch name isn't shown anywhere. If you've had a stack open for a while, you might forget the name of that branch and it's not trivial to find it again without doing some spelunking in git reflog.

It'd be great to have a git spr list command that shows all open stacks and/or include the branch name on open PRs to make it more discoverable.

[dekimsey]

FWIW, I think this is a duplicate of #235