docs: def write_version(path, ref=None):
      """Update version file using git desribe"""
      with lcd(dirname(path)):
          version = make_version(ref)
      if (env.get('full') or not os.path.exists(path)
              or version != open(path).read().strip()):
          with open(path, 'w') as out:
              out.write(version + '\n')
      return version