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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def gather_git_info(root, conf_rel_paths, whitelist_branches, whitelist_tags):
 """Gather info about the remote git repository. Get list of refs. :raise HandledError: If function fails with a handled error. Will be logged before raising. :param str root: Root directory of repository. :param iter conf_rel_paths: List of possible relative paths (to git root) of Sphinx conf.py (e.g. docs/conf.py). :param iter whitelist_branches: Optional list of patterns to filter branches by. :param iter whitelist_tags: Optional list of patterns to filter tags by. :return: Commits with docs. A list of tuples: (sha, name, kind, date, conf_rel_path). :rtype: list """

    log = logging.getLogger(__name__)

    # List remote.
    log.info('Getting list of all remote branches/tags...')
    try:
        remotes = list_remote(root)
    except GitError as exc:
        log.error(exc.message)
        log.error(exc.output)
        raise HandledError
    log.info('Found: %s', ' '.join(i[1] for i in remotes))

    # Filter and date.
    try:
        try:
            dates_paths = filter_and_date(root, conf_rel_paths, (i[0] for i in remotes))
        except GitError:
            log.info('Need to fetch from remote...')
            fetch_commits(root, remotes)
            try:
                dates_paths = filter_and_date(root, conf_rel_paths, (i[0] for i in remotes))
            except GitError as exc:
                log.error(exc.message)
                log.error(exc.output)
                raise HandledError
    except subprocess.CalledProcessError as exc:
        log.debug(json.dumps(dict(command=exc.cmd, cwd=root, code=exc.returncode, output=exc.output)))
        log.error('Failed to get dates for all remote commits.')
        raise HandledError
    filtered_remotes = [[i[0], i[1], i[2], ] + dates_paths[i[0]] for i in remotes if i[0] in dates_paths]
    log.info('With docs: %s', ' '.join(i[1] for i in filtered_remotes))
    if not whitelist_branches and not whitelist_tags:
        return filtered_remotes

    # Apply whitelist.
    whitelisted_remotes = list()
    for remote in filtered_remotes:
        if remote[2] == 'heads' and whitelist_branches:
            if not any(re.search(p, remote[1]) for p in whitelist_branches):
                continue
        if remote[2] == 'tags' and whitelist_tags:
            if not any(re.search(p, remote[1]) for p in whitelist_tags):
                continue
        whitelisted_remotes.append(remote)
    log.info('Passed whitelisting: %s', ' '.join(i[1] for i in whitelisted_remotes))

    return whitelisted_remotes