bug#27284: ‘guix pull’ builds using multiple derivations

[Ricardo Wurmus <rekado@elephly.net>]

Hi Ludo,

> After quite a bit of tweaking I’ve finally pushed this patch series to
> master.  So if you run ‘guix pull’ now, you’ll get the new
> multiple-derivation build.

This is really great!  I’m very happy that this is finally in the master
branch.  Thank you!

As discussed on IRC, there is a problem when running “guix pull” with an
older version of Guix that is still using Guile 2.0, which seems to be
adequately fixed by your patch:

--8<---------------cut here---------------start------------->8---
diff --git a/guix/self.scm b/guix/self.scm
index c9e4a4250..c19b0f6fb 100644
--- a/guix/self.scm
+++ b/guix/self.scm
@@ -88,7 +88,11 @@ GUILE-VERSION (\"2.0\" or \"2.2\"), or #f if none of the packages matches."
       ("bzip2"      (ref '(gnu packages compression) 'bzip2))
       ("xz"         (ref '(gnu packages compression) 'xz))
       ("guix"       (ref '(gnu packages package-management)
-                         'guix-register)))))
+                         'guix-register))
+      ("guile2.0-json" (ref '(gnu packages guile) 'guile2.0-json))
+      ("guile2.0-ssh"  (ref '(gnu packages ssh) 'guile2.0-ssh))
+      ("guile2.0-git"  (ref '(gnu packages guile) 'guile2.0-git))
+      (_               #f))))                     ;no such package

 \f
;;;
--8<---------------cut here---------------end--------------->8---

A remaining problem for me was that “(guix docker)” could not be built
because “(json)” was supposedly not available.

None of this seems to be a problem when using Guile 2.2.

>   • The “guix-packages” derivation is coarse-grain.  We could perhaps
>     automatically split it in clusters of modules by analyzing the (gnu
>     packages …) module graph.

I think we should do this anyway and try to split up large modules and
reduce inter-module dependencies.

> This works unlocks some of the stuff in <https://bugs.gnu.org/22629>, so
> I’ll try to focus on that now.

Exciting!

--
Ricardo