bug#74339: 30.0.92; CC Mode stomps C TS Mode

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

> No, that is the problem.  Have a look at major-mode-remap-defaults, and
> how c-ts-mode uses it to cause the symbol `c-mode' to start c-ts-mode in
> certain circumstances.  This is what I'm unhappy about.

In which way is this worse than what we have in Emacs-29 where loading
`c-ts-mode` does things like:

    (add-to-list 'auto-mode-alist
                 '("\\(\\.[chi]\\|\\.lex\\|\\.y\\(acc\\)?\\)\\'" . c-ts-mode))
    (add-to-list 'auto-mode-alist '("\\.x[pb]m\\'" . c-ts-mode))

?

> That "somehow" is the loading of c-ts-mode.  I think that even C-h f
> c-ts-mode counts as an "explicit indication" of a supposed preference for
> c-ts-mode, given that it loads c-ts-mode (if it actually does).

Yup, and the same happens in Emacs-29.

> I don't think the current mechanism is ready for the release of Emacs 30.

I don't see a regression here.

> We don't have fine enough control.  /* mode: c */ followed by /*
> c-basic-offset: 4 */ in the Local Variables: section is a sure sign that
> C Mode is intended, not a random C handling mode.

In your head, maybe.
I think for most users of other C modes (e.g. `c-ts-mode` or
`sm-c-mode`), the /* mode: c */ thingy just means that this file should
use their favorite major mode for C.

> What I think we're lacking is an explicit setting or command for the
> user to state what her preferred mode for C actually is.

You still haven't explained why the user's personal preference about the
major mode should be stated in the file.


        Stefan