function & mock_mount(array $fs, $mountpoint = '~/approot') {
		$mountpoint = str_replace('~', $this->mock_homedir, trim($mountpoint, '/'));
		$normalizedfs = $this->mock_normalize($fs);
		$path = & $this->mock_ensurepath($mountpoint);

		$this->mock_fsmerge($path, $normalizedfs);

		return $path;
	}