Empty branch output:
    # Empty branches
    git branch -D ipc2 # Empty.
    git branch -D m3 # Empty.
    
Empty branches that have origin/* as upstream will not be considered for deletion.

Provide distance from upstream in output, i.e.

    # Branch gypi-own - [master: ahead 1, behind 281]
    # Branch m2 - [master: ahead 1]

Review URL: https://chromiumcodereview.appspot.com/14446006

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@196249 0039d316-1c4b-4281-b951-d872f2087c98