bug#74361: [PATCH] New option xref-navigation-display-window-action

[Juri Linkov <juri@linkov.net>]

>> cmuscheme.el:
>>   (define-derived-mode inferior-scheme-mode comint-mode "Inferior Scheme"
>>    ...
>>     (pop-to-buffer "*scheme*" display-comint-buffer-action)
>> 
>> inf-lisp.el:
>>   (define-derived-mode inferior-lisp-mode comint-mode "Inferior Lisp"
>>    ...
>>     (pop-to-buffer "*inferior-lisp*" display-comint-buffer-action)
>> 
>> shell.el:
>>   (define-derived-mode shell-mode comint-mode "Shell"
>>    ...
>>     (pop-to-buffer buffer display-comint-buffer-action)
>
> Those are not the categories, those are the deprecated user options
> for which the categories are supposed to be a replacement we
> recommend:
>
>   (make-obsolete-variable
>    'display-comint-buffer-action
>    "use a `(category . comint)' condition in `display-buffer-alist'."
>    "30.1")

The categories are a replacement only for customization.
But all display-buffer calls should still contain
`(category . comint)' that currently presented
in these variables.  IOW, the variables currently
are used in two ways:
1. as the default values for display-buffer calls
2. as user options

But now customization is supposed to be only with
the help of `(category . comint)' in `display-buffer-alist'.
So these variable will be used only in display-buffer calls.

> So if some user wants to take our advice and modernize his/her
> customizations to use '(category . comint)' instead of
> display-comint-buffer-action, the customization will stop working for
> him/her when we remove those obsolete options in some future Emacs
> version.  Right?  Or what am I missing?

These are two possible solutions:
1. Demote these options to variables not intended for customization.
2. Move their current default values to display-buffer calls.