bug#68251: message-yank-buffer insert many copies of image

[Eli Zaretskii]

> Date: Thu, 04 Jan 2024 21:09:23 -0800
> From:  Joseph Turner via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> To reproduce:
> - ~emacs -Q~
> - Open an image in a buffer
> - Create another buffer, call ~M-x message-mode~
> - Run ~message-yank-buffer~, select the buffer with the image
> 
> Expected:
> 
> One image is inserted into the buffer.
> 
> Actual:
> 
> Many images are inserted into the buffer.

It isn't specific to images: it happens with any 'display' property
that spans more than one text line.  message-yank-buffer looks at
buffer text and ignores the 'display' properties, so it inserts every
line after quoting it, and this you get as many copies of the
'display' property as there are newlines in the text covered by the
'display' property.