bug#53294: 29.0.50; Indirect font changes incorrectly affecting original buffer

[Eli Zaretskii]

> From: Andrew Hyatt <ahyatt@gmail.com>
> Cc: 53294@debbugs.gnu.org
> Date: Sun, 16 Jan 2022 10:28:40 -0500
> 
> > But "inheriting" the state means the indirect buffer gets the 
> > copy of the variables of the original buffer, and that is not a 
> > deep copy, AFAIU. 
> > 
> > Stefan, any comments on this issue? 
> 
> Sorry, I may have been unclear. I'm not disagreeing - what you 
> just said is correct. But, because of that, it's a bug for code to 
> make an indirect buffer, then perform operations on it via setcdr 
> or setf like things, which then will affect the original buffer's 
> variables.

I'm not sure it's a bug.  It could be a "feature", not limited to
face-remapping-alist, but instead affecting every buffer-local
variable that is not a simple scalar.