code: public static Diff fromDelta(String text1, String delta)
              throws IllegalArgumentException {
          return new Diff(changesFromDelta(text1, delta), DiffOptions.defaults());
      }
docs: Given the original text1, and an encoded string which describes the
  operations required to transform text1 into text2, compute the full diff.
  
  @param text1 Source string for the diff.
  @param delta Delta text.
  @return Diff object.
  @throws IllegalArgumentException If invalid input.