code: def __get_files_to_be_added(self, repository):
          
          for root, dirs, files in os.walk(repository.working_dir):
              for f in files:
                  relative_path = os.path.join(root, f)[len(repository.working_dir) + 1:]
                  try:
                      repository.head.commit.tree[relative_path] # will fail if not tracked
                      yield relative_path
                  except:
                      pass
docs: :return: the files that have been modified and can be added