code: def create_git_action_for_new_collection(self, new_collection_id=None):
          
          ga = self.create_git_action()
          assert new_collection_id is not None
          # id should have been sorted out by the caller
          self.register_doc_id(ga, new_collection_id)
          return ga, new_collection_id
docs: Checks out master branch as a side effect