code: def pull(self, url):
          
          url = self._get_url(url)
          cmd = ['pull']
          cmd.append("--ff-only")
          cmd.append(url)
          cmd = ' '.join(cmd)
          # If error occurs run_git_command raises RepositoryError already
          self.run_git_command(cmd)
docs: Tries to pull changes from external location.