'Read git config value into the system, user and repo dicts.'

def _read_configs(self):

    self._map.clear()
    self._system.clear()
    self._user.clear()
    self._user_or_system.clear()
    self._repo.clear()
    self._all.clear()
    if (u'system' in self._config_files):
        self._system.update(self.read_config(self._config_files[u'system']))
    if (u'user' in self._config_files):
        self._user.update(self.read_config(self._config_files[u'user']))
    if (u'repo' in self._config_files):
        self._repo.update(self.read_config(self._config_files[u'repo']))
    for dct in (self._system, self._user):
        self._user_or_system.update(dct)
    for dct in (self._system, self._user, self._repo):
        self._all.update(dct)
