code: def log_append(self, oldbinsha, message, newbinsha=None):
          
          # NOTE: we use the committer of the currently active commit - this should be
          # correct to allow overriding the committer on a per-commit level.
          # See https://github.com/gitpython-developers/GitPython/pull/146
          try:
              committer_or_reader = self.commit.committer
          except ValueError:
              committer_or_reader = self.repo.config_reader()
          # end handle newly cloned repositories
          return RefLog.append_entry(committer_or_reader, RefLog.path(self), oldbinsha,
                                     (newbinsha is None and self.commit.binsha) or newbinsha,
                                     message)
docs: Append a logentry to the logfile of this ref
  
          :param oldbinsha: binary sha this ref used to point to
          :param message: A message describing the change
          :param newbinsha: The sha the ref points to now. If None, our current commit sha
              will be used
          :return: added RefLogEntry instance