bug#64212: 29.0.91; \Phi missing in TeX input method

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Roland Winkler <winkler@gnu.org>,  64212@debbugs.gnu.org
> Date: Thu, 22 Jun 2023 10:42:37 -0400
> 
> > If all that's needs to be added to the input method is
> >
> >    ("\\Phi" ?Φ)
> >
> > then I can do that.
> 
> That would work, but I think the problem was in the regexp and the patch
> below should fix it The Right Way.  Should I push it to `master` or are
> we still considering such fixes for `emacs-29`?

I'd prefer master.  Regular expressions, especially those which use
these constructs, are never without subtle aspects, and we have enough
issues on emacs-29 already, which keep me from releasing 29.1 for far
too long.  The problem, after all, is really minor at best.

Thanks.