static L<File> findAllFiles(L dirs) {
  ret findAllFiles(asObjectArray(dirs));
}

// dirs are String's or File's
static L<File> findAllFiles(O... dirs) {
  new L<File> l;
  for (O dir : dirs) {
    if (dir cast S && dir.endsWith("/."))
      // "/." means non-recurse
      for (File f : listFiles(dropSuffix("/.", dir)))
        l.add(f);
    else
      findAllFiles_impl(toFile(dir), l);
  }
  ret l;
}

static void findAllFiles_impl(File dir, L<File> l) {
  for (File f : listFiles(dir)) {
    l.add(f);
    if (f.isDirectory())
      findAllFiles_impl(f, l);
  }
}