bug#60176: 29.0.60; Fallback file variable mode if treesitter is not usable

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Cc: Eli Zaretskii <eliz@gnu.org>,  sadiq@sadiqpk.org,  60176@debbugs.gnu.org
> Date: Mon, 09 Jan 2023 19:30:20 +0200
> 
> Is it possible at least to make this forward-compatible to support
> such a predicate in future?  To enable ts-modes only in some buffers
> currently requires first to enable non-ts-mode, then conditionally ts-mode:
> 
> (add-hook 'find-file-hook
>           (lambda ()
>             (when (and (eq major-mode 'c-mode)
>                        ;; Unless in internal buffers:
>                        (not (string-prefix-p " " (buffer-name))))
>               (c-ts-mode))))
> 
> With a predicate in major-mode-remap-alist it would immediately
> enable the required mode:
> 
> (setq major-mode-remap-alist
>       '((c-mode . (lambda () (not (string-prefix-p " " (buffer-name))))
>                 c-ts-mode)))

Why do we need such hoops to jump through?  I think we should simply
add

 (add-to-list 'auto-mode-alist
              '("\\.[ch]\\'" . c-ts-mode))

to c-ts-mode.el (and similarly for C++), and that's it.