bug#54381: 29.0.50; Automatically load custom-file

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Mon, 14 Mar 2022 10:47:03 +0100
> Cc: 54381@debbugs.gnu.org
> 
> So if we add this user option, it'll have to default to nil, and in that
> case I don't see much point in the user option.  (Because people will
> have to `setq' it in their init files.)

I agree.

> If we introduced the `custom-file' variable today, we'd load it
> automatically, but I don't think it's possible to do so now without
> breaking stuff.
> 
> Anybody else got an opinion?

Would it perhaps help if we could support automatic loading of the
custom file if its basename was something special, or perhaps one of a
small number of fixed names?  If we choose a name that is unlikely to
be in wide use, all people will need is to rename their files (and
modify the init file).