[PATCH 1 of 4] store all heads of a branch in the branch cache

[David Soria Parra]

> +    def branchtags(self):
> +        '''return a dict where branch names map to the tipmost head of
> +        the branch'''
> +        return dict([ (k, v[-1]) for (k, v) in self._branchheads().items() ])

Maybe I'm a little pedantic, but I think we usually use
return dict([(k, v[-1]) for (k, v) in self._branchheads().items()])
and not
return dict([ (k, v[-1]) for (k, v) in self._branchheads().items() ])

Not sure if other people would care about that.

David