def render_git_describe(pieces):
    """TAG[-DISTANCE-gHEX][-dirty].

    Like 'git describe --tags --dirty --always'.

    Exceptions:
    1: no tags. HEX[-dirty]  (note: no 'g' prefix)
    """
    if pieces['closest-tag']:
        rendered = pieces['closest-tag']
        if pieces['distance']:
            rendered += '-%d-g%s' % (pieces['distance'], pieces['short'])
    else:
        rendered = pieces['short']
    if pieces['dirty']:
        rendered += '-dirty'
    return rendered
