Filter by Git repositories in Symfony Finder

example.php

<?php
declare(strict_types=!);

$filter = new \EliasHaeussler\App\Filter('app');
$finder = \Symfony\Component\Finder\Finder::create()
    ->in($filter->getBasePath())
    ->filter($filter->repositories());

foreach ($finder as $file) {
    echo 'Hello, my name is ' . $file->getBasename() . '!';
}

Filter.php

<?php
declare(strict_types=1);
namespace EliasHaeussler\App;

/*
 * Copyright (C) 2020 Elias Häußler <elias@haeussler.dev>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <https://www.gnu.org/licenses/>.
 */

/**
 * Filter class for use in combination with {@see \Symfony\Component\Finder\Finder::filter()}.
 *
 * @author Elias Häußler <elias@haeussler.dev>
 * @license GPL-3.0-or-later
 */
final class Filter
{
    /**
     * @var string[]
     */
    private static $knownRepositories = [];

    /**
     * @var string
     */
    private $basePath;

    public function __construct(string $basePath)
    {
        $this->basePath = $basePath;
    }

    /**
     * Build closure to filter for files in repositories only.
     *
     * @return \Closure
     */
    public function repositories(): \Closure
    {
        return function (\SplFileInfo $file): bool {
            if ($this->isWithinKnownRepository($file)) {
                return true;
            }
            if ($this->isWithinRepository($file)) {
                static::$knownRepositories[] = $this->determineBaseDirectory($file);
                return true;
            }
            return false;
        };
    }

    /**
     * Test whether a given file is located inside a known repository.
     *
     * @param \SplFileInfo $file
     * @return bool
     */
    private function isWithinKnownRepository(\SplFileInfo $file): bool
    {
        $realPath = rtrim($file->getRealPath(), DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR;
        foreach (static::$knownRepositories as $knownRepository) {
            if (strpos($realPath, rtrim($knownRepository, DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR) === 0) {
                return true;
            }
        }
        return false;
    }

    /**
     * Test whether a given file is located inside a Git repository.
     *
     * @param \SplFileInfo $file
     * @return bool
     */
    private function isWithinRepository(\SplFileInfo $file): bool
    {
        if (strpos($file->getRealPath(), $this->basePath) !== 0) {
            return false;
        }
        return file_exists(static::determineBaseDirectory($file) . DIRECTORY_SEPARATOR . '.git');
    }

    /**
     * Determine base directory of a given file within the current base path.
     *
     * @param \SplFileInfo $file
     * @return string
     */
    private function determineBaseDirectory(\SplFileInfo $file): string
    {
        $absolutePath = ltrim(substr($file->getRealPath(), strlen($this->basePath)), DIRECTORY_SEPARATOR);
        $repositoryName = explode(DIRECTORY_SEPARATOR, $absolutePath)[0];
        return rtrim($this->basePath, DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR . $repositoryName;
    }

    public function getBasePath(): string
    {
        return $this->basePath;
    }
}