'Classify git config files into \'system\', \'user\', and \'repo\'.
Populates self._configs with a list of the files in
reverse-precedence order.  self._config_files is populated with
{category: path} where category is one of \'system\', \'user\', or \'repo\'.'

def _find_config_files(self):

    statinfo = _stat_info()
    self._configs = [x[1] for x in statinfo]
    self._config_files = {}
    for (cat, path, mtime) in statinfo:
        self._config_files[cat] = path
