Re: master 19a3b499f84: ; * lisp/loadup.el: Don't prohibit advice when ls-lisp is loaded.

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: emacs-devel@gnu.org,  luangruo@yahoo.com
> Date: Wed, 06 Dec 2023 11:12:30 -0500
> 
> >> IOW, merge `insert-directory` and `ls-lisp--insert-directory`
> >> by allowing `insert-directory-program` to be nil
> >> (as a replacement for the `ls-lisp-use-insert-directory-program`
> >> boolean) in which case we use the ls-lisp code?
> >
> > So if some Lisp program out there sets insert-directory-program to a
> > non-nil value (probably intending to affect only Posix systems), Emacs
> > on MS-Windows will suddenly start using it instead of ls-lisp?
> >
> > In general, IMO it's too late to make changes in this arrangement that
> > would require users to switch to customizing a different user option.
> 
> Then we can change the code to keep the same config vars but to change
> `insert-directory` so it tests `ls-lisp-use-insert-directory-program`
> and delegates to `ls-lisp` if non-nil, IOW hardcode the effect of
> the advice.

If that can be done safely and cleanly, yes.  But then I wonder why we
decided to use advice all those years ago...