bug#35621: Simplify comparing guix challenge results

[Ludovic Courtès]

Hi!

Vagrant Cascadian <address@hidden> skribis:

> What about an argument to "guix challenge" that handles the downloading
> and unpacking to a temporary directory, and possibly another that also
> runs a comparison tool against the results. Maybe something like:
>
>   $ guix challenge --download-differences
>   /tmp/git-XXXXX/SUBSTITTE-X/...-git-2.5.0
>   /tmp/git-XXXXX/SUBSTITUTE-Y/...-git-2.5.0
>   /gnu/store/...-git-2.5.0
>
> Downloads and unpacks the substitutes, and outputs the resulting
> directories.
>
>
>   $ guix challenge --download-differences --compare-with="diffoscope ..."
>
> This would do the above, plus run diffoscope on the directories
> ... though I think diffoscope can only compare between two things at a
> time... so that might get difficult if many substitutes return results.

Sounds like a good idea.  Perhaps ‘--compare-with’ is actually enough
(it would also download things), dunno.

Ludo’.