bug#65380: [PATCH] Add command to copy contents in a diff-mode buffer

[Jim Porter]

On 8/20/2023 1:13 PM, Gregory Heytings wrote:
> > Some way of yanking a rectangular selection as though it were a normal 
> > region (or some way to put the rectangular selection on the normal 
> > kill ring) would be great, and would solve this in a more-general way.
>
> These commands exist: C-x r k to kill a rectangular selection, C-x r M-w 
> to save it, and C-x r y to yank it.

That's not quite what I mean. "C-x r y" ('yank-rectangle') yanks the 
rectangle *as a rectangle*. That is, if I just copied a rectangle with 5 
lines, and yank it with 'yank-rectangle', it will add it to the next 5 
existing lines. Instead, what I want is to insert 5 new lines.

For example, if my buffer is:

  Hello
  There
  World

And I copied this rectangle:

  1
  2

Then 'yank-rectangle' at the beginning of the buffer yields:

  1Hello
  2There
  World

But I want:

  1
  2
  Hello
  There
  World

The latter would be much more useful when trying to copy/yank a rect out 
of a diff buffer as in this report.