@NotNull
  public static List<String> notNullizeContentTitles(@NotNull List<String> mergeContentTitles) {
    String left = StringUtil.notNullize(ThreeSide.LEFT.select(mergeContentTitles), DiffBundle.message("merge.version.title.our"));
    String base = StringUtil.notNullize(ThreeSide.BASE.select(mergeContentTitles), DiffBundle.message("merge.version.title.base"));
    String right = StringUtil.notNullize(ThreeSide.RIGHT.select(mergeContentTitles), DiffBundle.message("merge.version.title.their"));
    return Arrays.asList(left, base, right);
  }
@NotNull
  public static List<String> notNullizeContentTitles(@NotNull List<String> mergeContentTitles)