:param tag:
            Checks out specified commit.
            If set to ``None`` the latest commit will be checked out
        :returns:
            A list of all commits, descending

def commit(self):
        '''
        :param tag:
            Checks out specified commit.
            If set to ``None`` the latest commit will be checked out
        :returns:
            A list of all commits, descending
        '''

        commit = self._log(num=-1, format='%H')
        if commit.get('returncode') == 0:
            return commit.get('stdout')