def normalize_repo_root_url(url):
    """Normalize a GitHub URL into the root repository URL.

    Parameters
    ----------
    url : `str`
        A GitHub URL

    Returns
    -------
    url : `str`
        Normalized URL of a GitHub repository.

    Examples
    --------
    >>> normalize_repo_root_url('https://github.com/lsst/LDM-151.git')
    'https://github.com/lsst/LDM-151'
    """
    # Strip the .git extension, if present
    if url.endswith('.git'):
        url = url[:-4]
    return url