static File backupFile(S path) {
  backupFile(newFile(path));
}

static File backupFile(File f) {
  if (isDirectory(f)) fail("Is a directory: " + f);
  if (!fileExists(f)) ret;
  File fBackup = makeFileNameUnique(newFile(deletedFilesDir(), uniqueFileNameUsingMD5_80_v2(f2s(f))));
  moveFile(f, fBackup);
  //saveTextFile(newFile(f2s(fBackup) + ".original-path"), f2s(f));
  ret fBackup;
}