bug#21523: 25.0.50; Undo with active region adds extra text

[Lars Ingebrigtsen]

Drew Adams <drew.adams@oracle.com> writes:

> The Subject line is not very clear.  Here is a recipe.  You decide
> whether the behavior is correct or a bug.  FWIW, this behavior is at
> least as old as Emacs 20 (with transient-mark-mode on).
>
> emacs -Q
>
> In buffer *scratch*, put point before "that" on the last line.
> `M-c', to capitalize "That".
> `C-SPC C-e', to select the text after "That", up to eol.
> (The region does not contain the word "That".)
>
> `C-_' to undo the last change within the region.
> The word "that" is inserted, giving this:
>
> ;; then enter the text in Thatthat file=A1=AFs own buffer.

This bug is still present in Emacs 28.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no