Re: Upgrading packages with substitutes only (bug #26608)

[ludo@gnu.org (Ludovic Courtès)]

Ricardo Wurmus <rekado@elephly.net> skribis:

> Ludovic Courtès <ludo@gnu.org> writes:
>
>> BTW, should --only-substitutes filter out packages without a substitute,
>> or should it simply stop and report the list of missing substitutes
>> (after which the user could use --do-not-upgrade)?
>
> In my opinion “--only-substitutes” should stop and report a list.
> If it continued without complaining there could be problems:
>
> * partial upgrades could leave the profile in an unusable state
>
> * an attacker could use this to trick a user into thinking that they
>   have all available updates

Agreed.

> On the other hand, it would make “--only-substitutes” less usable,
> because to actually perform work one would have to deal with the failure
> case.

IMO that’s OK.  “--only-substitutes” would typically be for interactive
use, when you’re in a hurry and you Understand The Risks (click on the
checkbox ;-)).  For unattended upgrades, I think one would want to
upgrade no matter what (assuming of course the build farm is not
completely broken, meaning that most substitutes are available.)

WDYT?

In the future I was also thinking that the build farm could tag Git
commits that it has fully built, and thus ‘guix pull’ could be told to
pull to the latest fully-built commit.

Ludo’.