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}