git-codereview: add [branchname] when on release branch
git-codereview: add [branchname] when on release branch

This behavior was changed by 2865802.

Change-Id: Ib5a254240d4e8a8254ce52929ed1ec2165d545e2
Reviewed-on: https://go-review.googlesource.com/24756
Reviewed-by: Chris Broadfoot <0c2851a4f8ab4aa5606e69c0757771dd13dbe686@golang.org>

golang/review