Separate field for branch in revision
Summary:
The main purpose of this change is to allow selecting the branch by
triple-click.
Plus it is not perfectly clear that the text in brackets means branch.
Test Plan: Display revision.
Reviewers: epriestley
Reviewed By: epriestley
CC: aran, epriestley
Differential Revision: https://secure.phabricator.com/D1585