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

[Gregory Heytings]

> > Yeah, the question then is: should it be new kill/copy commands or a 
> > new yank command?
>
> I would do something else: a command to move the killed rectangle to the 
> kill-ring.  And perhaps a command to do the opposite: transform the last 
> item of the kill-ring into a killed rectangle.

And here are the two commands I had in mind:

(defun move-killed-rectangle-to-kill-ring ()
  "Move the killed rectangle to the `kill-ring'."
  (interactive)
  (if killed-rectangle
      (with-temp-buffer
        (while killed-rectangle
          (insert-for-yank (car killed-rectangle))
          (insert "\n")
          (setq killed-rectangle (cdr killed-rectangle)))
        (kill-ring-save (point-min) (point-max)))
    (user-error "No killed rectangle")))

(defun copy-last-kill-to-killed-rectangle ()
  "Transform the current item of `kill-ring' into a killed rectangle"
  (interactive)
  (with-temp-buffer
    (let ((max -1))
      (insert-for-yank (current-kill 0 t))
      (goto-char (point-min))
      (while (not (eobp))
        (move-end-of-line nil)
        (let ((col (current-column)))
          (when (> col max)
            (setq max col)))
        (forward-line 1))
      (let ((col (current-column)))
        (when (< col max)
          (insert (make-string (- max col) ? ))))
    (kill-rectangle (point-min) (point-max)))))

WDYT?