def tag_versions(repo_path):
    """
    Given a repo will add a tag for each major version.

    Args:
        repo_path(str): path to the git repository to tag.
    """
    repo = dulwich.repo.Repo(repo_path)
    tags = get_tags(repo)
    maj_version = 0
    feat_version = 0
    fix_version = 0
    last_maj_version = 0
    last_feat_version = 0
    result = []

    for commit_sha, children in reversed(
            get_children_per_first_parent(repo_path).items()
    ):
        commit = get_repo_object(repo, commit_sha)
        maj_version, feat_version, fix_version = get_version(
            commit=commit,
            tags=tags,
            maj_version=maj_version,
            feat_version=feat_version,
            fix_version=fix_version,
            children=children,
        )
        if (
            last_maj_version != maj_version or
            last_feat_version != feat_version
        ):
            last_maj_version = maj_version
            last_feat_version = feat_version
            tag_name = 'refs/tags/v%d.%d' % (maj_version, feat_version)
            if ON_PYTHON3:
                repo[str.encode(tag_name)] = commit
            else:
                repo[tag_name] = commit

            result.append(
                'v%d.%d -> %s' % (maj_version, feat_version, commit_sha)
            )

    return '\n'.join(result)
Given a repo will add a tag for each major version.

    Args:
        repo_path(str): path to the git repository to tag.