def pack(directory, dest_dir, build_number):
    """Repack a previously unpacked wheel directory into a new wheel file.

    The .dist-info/WHEEL file must contain one or more tags so that the target
    wheel file name can be determined.

    :param directory: The unpacked wheel directory
    :param dest_dir: Destination directory (defaults to the current directory)
    """
    # Find the .dist-info directory
    dist_info_dirs = [fn for fn in os.listdir(directory)
                      if os.path.isdir(os.path.join(directory, fn)) and DIST_INFO_RE.match(fn)]
    if len(dist_info_dirs) > 1:
        raise WheelError('Multiple .dist-info directories found in {}'.format(directory))
    elif not dist_info_dirs:
        raise WheelError('No .dist-info directories found in {}'.format(directory))

    # Determine the target wheel filename
    dist_info_dir = dist_info_dirs[0]
    name_version = DIST_INFO_RE.match(dist_info_dir).group('namever')

    # Read the tags and the existing build number from .dist-info/WHEEL
    existing_build_number = None
    wheel_file_path = os.path.join(directory, dist_info_dir, 'WHEEL')
    with open(wheel_file_path) as f:
        tags = []
        for line in f:
            if line.startswith('Tag: '):
                tags.append(line.split(' ')[1].rstrip())
            elif line.startswith('Build: '):
                existing_build_number = line.split(' ')[1].rstrip()

        if not tags:
            raise WheelError('No tags present in {}/WHEEL; cannot determine target wheel filename'
                             .format(dist_info_dir))

    # Set the wheel file name and add/replace/remove the Build tag in .dist-info/WHEEL
    build_number = build_number if build_number is not None else existing_build_number
    if build_number is not None:
        if build_number:
            name_version += '-' + build_number

        if build_number != existing_build_number:
            replacement = ('Build: %s\r\n' % build_number).encode('ascii') if build_number else b''
            with open(wheel_file_path, 'rb+') as f:
                wheel_file_content = f.read()
                if not BUILD_NUM_RE.subn(replacement, wheel_file_content)[1]:
                    wheel_file_content += replacement

                f.truncate()
                f.write(wheel_file_content)

    # Reassemble the tags for the wheel file
    impls = sorted({tag.split('-')[0] for tag in tags})
    abivers = sorted({tag.split('-')[1] for tag in tags})
    platforms = sorted({tag.split('-')[2] for tag in tags})
    tagline = '-'.join(['.'.join(impls), '.'.join(abivers), '.'.join(platforms)])

    # Repack the wheel
    wheel_path = os.path.join(dest_dir, '{}-{}.whl'.format(name_version, tagline))
    with WheelFile(wheel_path, 'w') as wf:
        print("Repacking wheel as {}...".format(wheel_path), end='')
        sys.stdout.flush()
        wf.write_files(directory)

    print('OK')
Repack a previously unpacked wheel directory into a new wheel file.

    The .dist-info/WHEEL file must contain one or more tags so that the target
    wheel file name can be determined.

    :param directory: The unpacked wheel directory
    :param dest_dir: Destination directory (defaults to the current directory)
    
product/gradle-plugin/src/main/python/wheel/cli/pack.py