In [13]: repo.index.diff(None)Out[13]: [<git.diff.Diff at 0x10d0eab18>]In [14]: repo.index.diff(None, create_patch=True)Out[14]: [<git.diff.Diff at 0x10d0eaaa0>]

In [11]: repo.index.diff('HEAD~1', create_patch=True)---------------------------------------------------------------------------AttributeError                            Traceback (most recent call last)<ipython-input-11-49c4ff310661> in <module>()----> 1 repo.index.diff('HEAD~1', create_patch=True)/Library/Python/2.7/site-packages/git/index/util.pyc in check_default_index(self, *args, **kwargs)     62                 if self._file_path != self._index_path():     63                         raise AssertionError( "Cannot call %r on indices that do not represent the default git index" % func.__name__ )---> 64                 return func(self, *args, **kwargs)     65         # END wrpaper method     66 /Library/Python/2.7/site-packages/git/index/base.pyc in diff(self, other, paths, create_patch, **kwargs)   1146                         cur_val = kwargs.get('R', False)   1147                         kwargs['R'] = not cur_val-> 1148                         return other.diff(self.Index, paths, create_patch, **kwargs)   1149                 # END diff against other item handlin   1150/Library/Python/2.7/site-packages/git/diff.pyc in diff(self, other, paths, create_patch, **kwargs)     99                 if create_patch:    100                         diff_method = Diff._index_from_patch_format--> 101                 index = diff_method(self.repo, proc.stdout)    102    103                 status = proc.wait()/Library/Python/2.7/site-packages/git/diff.pyc in _index_from_patch_format(cls, repo, stream)    299                         a_path, b_path, similarity_index, rename_from, rename_to, \    300                                 old_mode, new_mode, new_file_mode, deleted_file_mode, \--> 301                                 a_blob_id, b_blob_id, b_mode = header.groups()    302                         new_file, deleted_file = bool(new_file_mode), bool(deleted_file_mode)    303AttributeError: 'NoneType' object has no attribute 'groups'