Reported in https://codereview.chromium.org/1852803002/#msg5.
Also some cleanup in nearby code AND fix of the git cl diff's previous behavior that actually updated local branch config with latest *uploaded* CL values. 

BUG=579182
R=machenbach@chromium.org,andybons@chromium.org
CC=servolk@chromium.org

Review URL: https://codereview.chromium.org/1871463003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@299759 0039d316-1c4b-4281-b951-d872f2087c98