old_contents: class Commit(object):
      def __init__(self, commit_id, author, time, message, files, diff):
          """
          comimt_id should be a string, author a string, time a datetime object,
          message a string, files a list of filenames (strings), and diff a
          string
          """
          self.commit_id = commit_id
          self.author = author
          self.time = time
          self.message = message
          self.files = files
          self.diff = diff
  
      def _get_diff(self):
          if callable(self._diff):
              self._diff = self._diff()
          return self._diff
  
      def _set_diff(self, diff):
          self._diff = diff
  
      diff = property(_get_diff, _set_diff)
  
      def __str__(self):
          return "<Commit %s by %s on %s>" % (self.commit_id, self.author, self.time)
  
      __repr__ = __str__
  
new_contents: class Commit(object):
      def __init__(self, commit_id, author, time, message, files, diff):
          """
          commit_id should be a string, author a string, time a datetime object,
          message a string, files a list of filenames (strings), and diff a
          string
          """
          self.commit_id = commit_id
          self.author = author
          self.time = time
          self.message = message
          self.files = files
          self.diff = diff
  
      def _get_diff(self):
          if callable(self._diff):
              self._diff = self._diff()
          return self._diff
  
      def _set_diff(self, diff):
          self._diff = diff
  
      diff = property(_get_diff, _set_diff)
  
      def __str__(self):
          return "<Commit %s by %s on %s>" % (self.commit_id, self.author, self.time)
  
      __repr__ = __str__
  
subject: Fix typo.