# File lib/rbreadline.rb, line 5374
  def rl_maybe_replace_line()
    temp = current_history()
    # If the current line has changed, save the changes.
    if (temp && temp.data != @rl_undo_list)
      temp = replace_history_entry(where_history(), @rl_line_buffer, @rl_undo_list)
    end
    0
  end