docs: def _version_find_existing():
      """Returns set of existing versions in this repository.  This
      information is backed by previously used version tags in git.
      Available tags are pulled from origin repository before.
  
      :return:
          available versions
      :rtype:
          set
      """
      _tool_run('git fetch origin -t')
      git_tags = [x for x in (y.strip() for y in (_tool_run('git tag -l')
                                                  .stdout.split('\n'))) if x]
      return {tuple(int(n) if n else 0 for n in m.groups())
              for m in (_version_re.match(t) for t in git_tags) if m}