docs: private LinkedList<Change> bisectSplit(String text1, String text2,
                                             int x, int y) {
          String text1a = text1.substring(0, x);
          String text2a = text2.substring(0, y);
          String text1b = text1.substring(x);
          String text2b = text2.substring(y);
  
          // Compute both diffs serially.
          LinkedList<Change> diffs = main(text1a, text2a, false);
          LinkedList<Change> diffsb = main(text1b, text2b, false);
  
          diffs.addAll(diffsb);
          return diffs;
      }