D5475: branch:Added option to show branch name of a given rev (Issue5948)

[Yuya Nishihara]

>   Thanks for the info @yuja. I'm thinking to move --rev/-r to branches command and replacing --show/-s that I've made to --rev/-r in the branch command itself.

I'm not sure if I get it, but my idea is to add `hg branches -r/--rev`
that selects branches to be listed by revisions. So, `hg branch -srREV` in
your original patch will be equivalent to `hg branches -qrREV` (-q to
suppress detailed output.)