checkout example

$this->assertInstanceOf(\DateTimeImmutable::class, $git->getLastAuthoredDate());
        $this->assertStringMatchesFormat('v%s', $git->getLastTag());
        $this->assertStringMatchesFormat('v3%s', $git->getLastTag(fn ($tag) => str_starts_with($tag, 'v3')));
    }

    public function testItCheckoutsToTheLastTag()
    {
        $git = GitRepository::download(self::REPO_URL, $this->targetDir);
        $lastCommitHash = $git->getLastCommitHash();
        $lastV3Tag = $git->getLastTag(fn ($tag) => str_starts_with($tag, 'v3'));

        $git->checkout($lastV3Tag);

        $this->assertNotEquals($lastCommitHash, $git->getLastCommitHash());
    }
}

$repoDir = sys_get_temp_dir().'/icu-data';
    $git = GitRepository::download('https://github.com/unicode-org/icu.git', $repoDir);

    echo "Git clone to {$repoDir} complete.\n";
}

$gitTag = $git->getLastTag(fn ($tag) => preg_match('#^release-[0-9]{1,}-[0-9]{1}$#', $tag));
$shortIcuVersion = strip_minor_versions(preg_replace('#release-([0-9]{1,})-([0-9]{1,})#', '$1.$2', $gitTag));

echo "Checking out `{$gitTag}` for version `{$shortIcuVersion}`...\n";
$git->checkout('tags/'.$gitTag);

$filesystem = new Filesystem();
$sourceDir = $repoDir.'/icu4c/source';

if ($argc >= 3) {
    $buildDir = $argv[2];
} else {
    // Always build genrb so that we can determine the ICU version of the     // download by running genrb --version     echo "Building genrb.\n";