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

["Ludovic Courtès" <ludo@gnu.org>]

Hi,

Csepp <raingloom@riseup.net> skribis:

> 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.

I understand this is a source of confusion.  It has to do with “grafts”
(which themselves are about applying security updates): if substitutes
for a package are missing, Guix has a partial view of the dependency
graph, which is why it can only tell you about extra builds/downloads
later on in the process (it does report them, only later).

(If you’re curious, see
<https://guix.gnu.org/en/blog/2020/grafts-continued/> for details.)

Thanks,
Ludo’.