bug#44232: global-display-fill-column-indicator-mode vs. readonly buffers

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: jidanni@jidanni.org,  44232@debbugs.gnu.org
> Date: Mon, 26 Oct 2020 17:19:25 +0100
> 
> Example:
>       (c-mode c++-mode)
> means that Highlight Changes mode is turned on for buffers in C and C++
> modes only.
> ---
> 
> So it's a complex
> 
> (c-mode (not text-mode) ...)

I proposed something simpler: a list of modes where
display-fill-column-indicator-mode will NOT be turned on automatically
by the globalized minor mode.

> (Although I'd say use derived-mode-p instead of eq to check.)

Yes, of course.