bug#70587: More buffers that ought to be read-only

[Eli Zaretskii <eliz@gnu.org>]

> From: Dan Jacobson <jidanni@jidanni.org>
> Date: Fri, 26 Apr 2024 09:16:08 +0800
> 
> diff-default-read-only is a variable defined in ‘diff-mode.el’.
> Its value is nil
> If non-nil, ‘diff-mode’ buffers default to being read-only.
> 
> That's funny, it seems they are already read-only, without setting this
> variable. Maybe this variable can be retired.

I cannot reproduce this.  E.g., visiting a file that turned on
diff-mode doesn't make the buffer read-only.  So please show a recipe,
preferably starting from "emacs -Q", where a diff-mode buffer is
read-only without changing this variable from its default value of
nil.

> But how about *Shell Command Output*, and errors buffers, they should be
> read-only by default too.
> 
> Why? Because tons of times we realize for the last half hour we have
> been editing our program's output buffer instead of the source code.
> 
> (Often due to using sh -x or make (without -s) which echo command
> lines.)

A simple "C-x C-q" should set you up, in those cases.

Emacs cannot possibly cater to each and every use case out there.
Sometimes you need to do stuff manually, if your case is specialized
to require that.