@NotNull
  private static Change createChange(@NotNull DiffRequest request) {
    Change change = request.getUserData(ChangeDiffRequestProducer.CHANGE_KEY);
    if (change != null) return change;

    List<DiffContent> contents = ((ContentDiffRequest)request).getContents();
    List<@Nls String> titles = ((ContentDiffRequest)request).getContentTitles();
    assert contents.size() == 2;
    String bTitle = ObjectUtils.chooseNotNull(titles.get(0), DiffBundle.message("diff.version.title.before"));
    String aTitle = ObjectUtils.chooseNotNull(titles.get(1), DiffBundle.message("diff.version.title.after"));
    ContentRevision bRev = createRevision(contents.get(0), bTitle);
    ContentRevision aRev = createRevision(contents.get(1), aTitle);
    return new Change(bRev, aRev);
  }
@NotNull
  private static Change createChange(@NotNull DiffRequest request)