bug#47424: 28.0.50; enable-theme shows an empty list

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Sun, 4 Apr 2021 08:17:04 -0500
> Cc: monnier@iro.umontreal.ca, 47424@debbugs.gnu.org, mardani29@yahoo.es
> 
> To put this more concretely, I'd like to see two functions (and let's
> disregard what we have now for the sake of argument):
> 
>     enable-theme
>     disable-theme
> 
> Whatever happens technically (loading, autoloading, unloading, etc.) is
> not interesting to the user.  What is interesting is that after you run
> one of the above commands the specified theme is either enabled or
> disabled.

This (a) turns the table on what we currently do, since currently
load-theme can optionally enable the theme, while you propose to do it
the other way around; (b) rocks the very delicate boat of how themes
are enable, disabled, and prioritized and how they interact with face
setup, so if we go that way, we should expect quite a rocky ride
(suggested reading: custom.el).  Is it really worth that?