bug#35872: messages that are redundant can be eliminated?

["Ludovic Courtès" <ludo@gnu.org>]

Hi!

Ludovic Courtès <ludo@gnu.org> skribis:

> (+Cc: Efraim following our discussion on IRC.)
>
> Ludovic Courtès <ludo@gnu.org> skribis:
>
>> This is a bug where the presence of propagated inputs leads ‘guix
>> upgrade’ to assume something would be upgraded, even when that’s not the
>> case.  This can be reproduced with:
>>
>>   guix install -p foo guile
>>   guix upgrade -p foo
>
> I came up with an actual fix for that (attached), nice and clean, which
> would allow ‘guix upgrade’ to correctly determine whether something is
> going to be upgraded.
>
> But then I realized that this cannot work in the presence of grafts:
> first because ‘-n’ currently implies ‘--no-grafts’, so this is an apple
> to orange comparison, and then because computing the output file name of
> a grafted package can require building the package (grafts are “dynamic
> dependencies”.)

I saw the light :-) and came up with a simple solution to this in commit
a357849f5b1314c2a35efeee237645b9b08c39f5.  Basically, we do the complete
manifest entry comparison as in the patch I posted earlier, but we punt
if doing so would require building things (for grafts).

Anecdotal data: on my 288-item profile, “guix upgrade -n” would
previously report that 124 things need to be upgraded, and now it
reports 97 instead.

Ludo’.