[ruby/reline] Show all lines higher than the screen when finished

On Unix-like OSes, logs prior to the screen are not editable. When the code
is higher than the screen, the code is only shown on the screen until input
is finished, but when it is finished, all lines are outputted.

ruby/reline@8cd9132a39

lib/reline/line_editor.rb

@@ -388,6 +388,19 @@ def rerender
       @cleared = false
       return
     end
+    if @is_multiline and finished? and @scroll_partial_screen
+      # Re-output all code higher than the screen when finished.
+      Reline::IOGate.move_cursor_up(@first_line_started_from + @started_from - @scroll_partial_screen)
+      Reline::IOGate.move_cursor_column(0)
+      @scroll_partial_screen = nil
+      prompt, prompt_width, prompt_list = check_multiline_prompt(whole_lines, prompt)
+      modify_lines(whole_lines).each_with_index do |line, index|
+        @output.write "#{prompt_list ? prompt_list[index] : prompt}#{line}\n"
+        Reline::IOGate.erase_after_cursor
+      end
+      @output.flush
+      return
+    end
     new_highest_in_this = calculate_height_by_width(prompt_width + calculate_width(@line.nil? ? '' : @line))
     # FIXME: end of logical line sometimes breaks
     rendered = false