bug#13824: 24.3.50; :package-version not taking priority over :version

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Thu, 8 Aug 2019 05:59:21 +0200
> Cc: 13824@debbugs.gnu.org
> 
> Bastien Guerry <bzg@altern.org> writes:
> 
> > The docstring of `defcustom' says:
> >
> > :package-version
> >         VALUE should be a list with the form (PACKAGE . VERSION)
> >         specifying that the variable was first introduced, or its
> >         default value was changed, in PACKAGE version VERSION.  This
> >         keyword takes priority over :version.
> >         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >
> > but `describe-variable-custom-version-info' gives priority to :version
> > over :package-version.  Which one is correct here?
> 
> This is still an issue on current master (and 26.2).
> 
> I reproduced this using:
> 
>     (progn
>       (defcustom foobar nil
>         "foo"
>         :version "27.1"
>         :package-version '(foo . "1"))
>       (describe-variable-custom-version-info 'foobar))
> 
> Which results in:
> 
>     "This variable was introduced, or its default value was changed, in
>     version 27.1 of Emacs.
>     "
> 
> But C-h f defcustom says:
> 
>     :package-version
>             VALUE should be a list with the form (PACKAGE . VERSION)
>             specifying that the variable was first introduced, or its
>             default value was changed, in PACKAGE version VERSION.  This
>             keyword takes priority over :version.

The implementation only prefers :package-version for the purposes of
customize-changed-options, i.e. the Options->Customize Emacs->New
Options menu item.  By contrast, describe-variable-custom-version-info
is used for displaying the doc strings of options.  For a package that
is bundled with Emacs, I think displaying :version in "C-h v" makes
sense.  If people agree, then this is a minor documentation bug (also
to be fixed in the ELisp manual), not a code bug.

Bill, what is your take on this?  Your change, which introduced this
attribute, only modified customize-changed-options.  Was that on
purpose?