// returns true if file was changed
sbool cleanFluidTextFile(File f, O... _) {
  optPar bool withBackup;
  optPar
  new CleanFluidTextFile cleaner;
  {
    temp Reader reader = utf8reader(f);
    cleaner.reader = reader;
    cleaner.read();
  }
  new StringWriter writer;
  cleaner.writer = writer;
  cleaner.write();
  S out = str(writer);
  if (eq(loadTextFile(f), out)) false;
  if (withBackup)
    print("Backed file up to " + renameFileToSomeBackupName(f, "fluidClean"));
  saveTextFile(f, out);
  true;
}