def stat_ahead_behind(git, local_ref, remote_ref):
    """
    Returns a tuple (ahead, behind) describing how far
    from the remote ref the local ref is.
    """
    behind = 0
    ahead = 0
    ret, out = git.call('rev-list', '--left-right', '%s..%s' % (remote_ref,
        local_ref), raises=False)
    if ret == 0:
        ahead = len(out.split())
    ret, out = git.call('rev-list', '--left-right', '%s..%s' % (local_ref,
        remote_ref), raises=False)
    if ret == 0:
        behind = len(out.split())
    return ahead, behind
