bug#41930: ‘guix pull’ shows raw build log output

[Ludovic Courtès]

Ludovic Courtès <ludo@gnu.org> skribis:

> The attached patch fixes that in an unimaginative but efficient fashion:
>
>   1. the parent process (which runs ‘build-self.scm’) accepts connections on
>      a named socket;
>
>   2. the ‘compute-guix-derivation’ process connects to that socket and
>      sends it its raw build output (what we see in the snippet above);
>
>   3. the parent process reads that and sends it to its own
>      (current-build-output-port); that port processes those “@” build
>      traces according to the current ‘--verbosity’—see (guix status).
>
> With this in place, builds or downloads triggered during the evaluation
> of ‘compute-guix-derivation’ are reported in a consistent way from a UI
> viewpoint.
>
> There was one remaining glitch: the spinner that
> ‘compute-guix-derivation’ prints would show up in the middle of the
> prettified build output.  The second patch addresses that.

Pushed as a81a19930b2cbe1327e1e82d6210f80846ce2898.

Ludo’.