> It just occurred to me that it might be more intuitive to use one of

>   'interactive
>   #f   ; never download
>   _    ; (any other value) always download

IMO, an attached version is better because we use high-level terms:
interactive, never, and always.

> Modulo these details, it seems ready to get it.

Can I push the attached version?

What should I do next?  For instance, I can change 'guix refresh' to
fetch signatures first and don't download tarballs that can't be
authenticated (when signatures are missing and 'never' is used).  Or I
can fix it not to mix version numbers (not to update Guile 1.8.8 to
version 2.0.9).