public function addSubdirectory($sitePath)
    {
        $paths = array_map(function ($subDir) use ($sitePath) {
            return "$sitePath/$subDir";
        }, $this->possibleSubdirectories());

        $foundPaths = array_filter($paths, function ($path) {
            return file_exists($path);
        });

        // If paths are found, return the first one.
        if (!empty($foundPaths)) {
            return array_shift($foundPaths);
        }

        // If there are no matches, return the original path.
        return $sitePath;
    }