Checks out master branch as a side effect

def create_git_action_for_new_study(self, new_study_id=None):
        """Checks out master branch as a side effect"""
        ga = self.create_git_action()
        if new_study_id is None:
            new_study_id = self._mint_new_study_id()
        self.register_doc_id(ga, new_study_id)
        return ga, new_study_id