bug#13780: 24.2; Making find-file-hook customizable seems to cause troublle

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Tue, 24 Nov 2020 18:18:58 -0800
> Cc: 13780@debbugs.gnu.org, monnier@iro.umontreal.ca, rrt@sc3d.org
> 
> Stefan Monnier <monnier@iro.umontreal.ca> writes:
> 
> >>> So until Custom is fixed to actually properly handle customisation of
> >>> hooks (e.g. by storing "add functions foo, bar, and baz" rather than
> >>> "ignore current value and just set it to (foo bar baz)").
> >> This sentence seems to be missing its main clause…
> >
> > That's not just an appearance.  Its main clause is:
> >
> >    So until Custom ...blabla... I think it's better to use defcustom for
> >    hooks very sparingly, i.e. only for those hook we can reasonably
> >    expect will only be modified by the user's customization.

IMO, this rationale is good for future additions, not for
already-existing user options.  We cannot un-defcustom a user option
just because someone became confused by some subtle use case.  This is
the price we pay for the flexibility and power we have in Emacs.