match: drop unnecessary removal of '.' from excluded roots The repo root is nothing special when it comes to what directories to visit: patterns like '-X relglob:*.py' should not exclude the top directory, while '-X path:.' should (pointless as such a pattern may be). The explicit removal of '.' from the set of excluded roots was probably there to avoid removing the the root directory when any patterns had been given, but since 20ad936ac5d2 (treemanifest: visit directory 'foo' when given e.g. '-X foo/ba?', 2015-05-27), we only exclude directories that should be completely excluded, so we no longer need to special-case the root directory.