@Override
    public int hashCode() {
      final int prime = 31;
      int result = (operation == null) ? 0 : operation.hashCode();
      result += prime * ((text == null) ? 0 : text.hashCode());
      return result;
    }
Create a numeric hash value for a Diff.
This function is not used by DMP.

@return Hash value.
src/burp/Utils/diff_match_patch.java