Fixes to roll_deps for the bots

The bots are running an older version of git which does not support the
-q/--quiet flag for branch or the --short flag for symbolic-ref.

BUG=
R=halcanary@google.com

Review URL: https://codereview.chromium.org/134723002

git-svn-id: http://skia.googlecode.com/svn/trunk@13030 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed