Decode string to configuration dict.

    Only values defined in settings._ALLOWED_MERGES can be redefined.

def _decode_config(conf_str):
    """
    Decode string to configuration dict.

    Only values defined in settings._ALLOWED_MERGES can be redefined.
    """
    conf_str = conf_str.strip()

    # convert "tttff" -> [True, True, True, False, False]
    conf = map(
        lambda x: True if x.upper() == "T" else False,
        list(conf_str)
    )

    return dict(zip(settings._ALLOWED_MERGES, conf))