bug#57315: guix upgrade --dry-run output is basically useless

[Csepp]

I'd like to figure out what Guix will try to build before I run an
upgrade on my netbook, so I always use --dry-run.  I'm pretty sure in
the past it used to show more information, but today it just showed that
it will download 20 megs, without saying what package that 20 megs are
for, which ones will be built, which ones are downloaded, or anything
useful at all.

And now I see it's building Caja.  Why did it not warn me beforehand?
No idea.

This should go without saying, but this is pretty bad UX.

Is there something that can be done about this?  The upgrade process on
less powerful machines is pretty awful currently.

Side note: I plan to work on a patch that adds an option to upgrade that
keeps everything that would require local building at its previous
version.  Hopefully I won't need to use the --do-not-upgrade option
after that.  Right now upgrading is a multi-hour manual process, which
honestly sucks.  With that patch it would still take a while but at
least it would run automatically.