[Filesystem] mirror() incorrectly skips files when copying from a child directory to a parent directory #32089
Description
Symfony version(s) affected: 4.3+
Description
When trying to mirror a child dir into a parent dir, a check in mirror() causes all file copies to be skipped.
How to reproduce
$filesystem = new \Symfony\Component\Filesystem\Filesystem();
$dir1 = __DIR__ . '/dir1/';
$dir2 = __DIR__ . '/dir1/dir2';
mkdir($dir1);
mkdir($dir2);
touch($dir1 . '/somefile.txt');
// Fails to copy because str_pos($dir2, $dir1) === 0 on line 575 in Filesystem()
$filesystem->mirror($dir2, $dir1);