static String getReplaceActionId(@NotNull ThreeSide master, @NotNull ThreeSide modifiedSide) {
    if (master == ThreeSide.LEFT && modifiedSide == ThreeSide.BASE) return "Diff.ApplyLeftSide";
    if (master == ThreeSide.RIGHT && modifiedSide == ThreeSide.BASE) return "Diff.ApplyRightSide";
    return null;
  }
static String getReplaceActionId(@NotNull ThreeSide master, @NotNull ThreeSide modifiedSide)