docs: def call_git_branch():
      """return the string output of git desribe"""
      try:
          with open(devnull, "w") as fnull:
              arguments = [GIT_COMMAND, 'rev-parse', '--abbrev-ref', 'HEAD']
              return check_output(arguments, cwd=CURRENT_DIRECTORY,
                                  stderr=fnull).decode("ascii").strip()
      except (OSError, CalledProcessError):
          return None