code: def clone_with_new_dockerfile(self, conf, docker_file):
          
          log.info("Copying context to add a different dockerfile")
          self.close()
          with a_temp_file() as tmpfile:
              old_t = os.stat(self.tmpfile.name).st_size > 0
              if old_t:
                  shutil.copy(self.tmpfile.name, tmpfile.name)
  
              with tarfile.open(tmpfile.name, mode="a") as t:
                  conf.add_docker_file_to_tarfile(docker_file, t)
                  yield ContextWrapper(t, tmpfile)
docs: Clone this tarfile and add in another filename before closing the new tar and returning