Subject: ci: Remove hydra support.

From: Mathieu Othacehe <[email-masked]>
Date: Wed, 17 Feb 2021 09:42:01 +0100

Hello,

This removes hydra support to use Cuirass as the only continuous
integration system. It also simplifies the evaluation process. Here's
how it's working now:

* Cuirass fetches new commits and calls its "evaluate" process.

* The "evaluate" process calls the "cuirass-jobs" procedure in the
newly checkouted Guix "build-aux/cuirass/gnu-system.scm" file.

* The "hydra-jobs" procedure in "build-aux/hydra/gnu-system.scm" file
  starts the evaluation of "hydra-jobs" of (gnu ci) module in an
  inferior using the new commit.

* This procedure returns the list of all the package derivations at that
  very commit under Hydra job format.

* This list is converted to the Cuirass job format and written on the
  stdout port.

* The main Cuirass process reads the "evaluate" output using a pipe, and
  registers the derivation that needs to be built in database.

This is quite complex and it requires to pass around a huge list of
jobs, consuming a lot of memory.

Here's the simplified method:

* The first two steps are identical.

* The "cuirass-jobs" procedure starts the evaluation of "cuirass-jobs"
  of (gnu ci) module in an inferior using the new commit. This procedure
  is passed a registration callback that directly registers the given
  jobs in database. It doesn't return anything.

As the "register" procedure is a part of Cuirass, the inversion on
control caused by the inferior is problematic. I had to proxy the
registration requests from the inferior to the evaluation process using
a named pipe.

Other than that, the process seems now less obfuscated.

Thanks,

Mathieu
>From c980a4a1357ca96c523e45b904cb2c2c1ead5b40 Mon Sep 17 00:00:00 2001
From: Mathieu Othacehe <[email-masked]>
Date: Sun, 14 Feb 2021 17:34:49 +0100
Subject: [PATCH] ci: Remove hydra support.

This removes hydra support to use Cuirass as the only continuous integration
system. It also changes the way jobs are transmitted to Cuirass. The
"cuirass-jobs" procedure no longer returns jobs. Instead it is passed a
"register" callback that can be called to register jobs.

This decreases the memory consumption and increases the evaluation speed as
there's no need to operate a possibly huge list of jobs anymore.

* build-aux/hydra/gnu-system.scm: Remove it.
* build-aux/hydra/guix-modular.scm: Ditto.
* build-aux/hydra/guix.scm: Ditto.
* build-aux/cuirass/hydra-to-cuirass.scm: Ditto.
* Makefile.am (EXTRA_DIST): Update it.
(hydra-jobs.scm): Remove it.
(cuirass-jobs.scm): Update it.
* build-aux/hydra/evaluate.scm: Move it to ...
* build-aux/cuirass/evaluate.scm: ... here.
* build-aux/cuirass/guix-modular.scm: Adapt it to use the Cuirass register
procedure.
* build-aux/cuirass/gnu-system.scm: Ditto.
* gnu/ci.scm (package->alist): Remove it.
(register-job-from-drv): New procedure.
(package-job, package-cross-job, cross-jobs, image-jobs, system-test-jobs,
tarball-jobs): Add a register arguments and pass it to
"register-job-from-drv" procedure.
(hydra-jobs): Rename it to ...
(cuirass-jobs): ... this procedure. Also add a register argument.
---
 Makefile.am                               |  17 +-
 build-aux/{hydra => cuirass}/evaluate.scm |  30 +-
 build-aux/cuirass/gnu-system.scm          |  93 ++++-
 build-aux/cuirass/guix-modular.scm        |  83 ++++-
 build-aux/cuirass/hydra-to-cuirass.scm    |  47 ---
 build-aux/hydra/gnu-system.scm            |  88 -----
 build-aux/hydra/guix-modular.scm          |  91 -----
 build-aux/hydra/guix.scm                  | 106 ------
 gnu/ci.scm                                | 429 ++++++++++------------
 9 files changed, 373 insertions(+), 611 deletions(-)
 rename build-aux/{hydra => cuirass}/evaluate.scm (82%)
 delete mode 100644 build-aux/cuirass/hydra-to-cuirass.scm
 delete mode 100644 build-aux/hydra/gnu-system.scm
 delete mode 100644 build-aux/hydra/guix-modular.scm
 delete mode 100644 build-aux/hydra/guix.scm

diff --git a/Makefile.am b/Makefile.am
index 52537fb53d..85307707d6 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -603,14 +603,9 @@ EXTRA_DIST +=						\
   etc/historical-authorizations				\
   build-aux/build-self.scm				\
   build-aux/compile-all.scm				\
-  build-aux/hydra/evaluate.scm				\
-  build-aux/hydra/gnu-system.scm			\
-  build-aux/hydra/guix.scm				\
-  build-aux/hydra/guix-modular.scm			\
   build-aux/cuirass/gnu-system.scm			\
   build-aux/cuirass/guix-modular.scm			\
   build-aux/cuirass/hurd-manifest.scm			\
-  build-aux/cuirass/hydra-to-cuirass.scm		\
   build-aux/check-final-inputs-self-contained.scm	\
   build-aux/check-channel-news.scm			\
   build-aux/compile-as-derivation.scm			\
@@ -950,21 +945,13 @@ check-channel-news: $(GOBJECTS)
 	$(AM_V_at)$(top_builddir)/pre-inst-env "$(GUILE)"	\
 	  "$(top_srcdir)/build-aux/check-channel-news.scm"
 
-# Compute the Hydra jobs and write them in the target file.
-hydra-jobs.scm: $(GOBJECTS)
-	$(AM_V_at)$(MKDIR_P) "`dirname "$@"`"
-	$(AM_V_GEN)$(top_builddir)/pre-inst-env "$(GUILE)"		\
-	  "$(top_srcdir)/build-aux/hydra/evaluate.scm"			\
-	  "$(top_srcdir)/build-aux/hydra/gnu-system.scm" > "$@.tmp"
-	$(AM_V_at)mv "$@.tmp" "$@"
-
 # Compute the Cuirass jobs and write them in the target file.
 cuirass-jobs.scm: $(GOBJECTS)
 	$(AM_V_at)$(MKDIR_P) "`dirname "$@"`"
 	$(AM_V_GEN)$(top_builddir)/pre-inst-env "$(GUILE)"		\
-	  "$(top_srcdir)/build-aux/hydra/evaluate.scm"			\
+	  "$(top_srcdir)/build-aux/cuirass/evaluate.scm"			\
 	  "$(top_srcdir)/build-aux/cuirass/gnu-system.scm" 		\
-	  cuirass > "$@.tmp"
+	  "$@.tmp"
 	$(AM_V_at)mv "$@.tmp" "$@"
 
 .PHONY: gen-ChangeLog gen-AUTHORS gen-tarball-version
diff --git a/build-aux/hydra/evaluate.scm b/build-aux/cuirass/evaluate.scm
similarity index 82%
rename from build-aux/hydra/evaluate.scm
rename to build-aux/cuirass/evaluate.scm
index c74fcdb763..f2ad67a104 100644
--- a/build-aux/hydra/evaluate.scm
+++ b/build-aux/cuirass/evaluate.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2016, 2017, 2018, 2020 Ludovic Courtès <[email-masked]>
 ;;; Copyright © 2017 Jan Nieuwenhuizen <[email-masked]>
+;;; Copyright © 2021 Mathieu Othacehe <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -73,7 +74,7 @@ Otherwise return THING."
 
 ;; Without further ado...
 (match (command-line)
-  ((command file cuirass? ...)
+  ((command file output)
    ;; Load FILE, a Scheme file that defines Hydra jobs.
    (let ((port (current-output-port))
          (real-build-things build-things))
@@ -91,7 +92,7 @@ Otherwise return THING."
          ;; Add %TOP-SRCDIR to the store with a proper Git predicate so we work
          ;; from a clean checkout
          (let ((source (add-to-store store "guix-source" #t
-                                     "sha256" %top-srcdir
+                                    "sha256" %top-srcdir
                                      #:select? (git-predicate %top-srcdir))))
            (with-directory-excursion source
              (save-module-excursion
@@ -102,23 +103,13 @@ Otherwise return THING."
                         file source)
                 (primitive-load file))))
 
-           ;; Call the entry point of FILE and print the resulting job sexp.
-           (pretty-print
-            (match ((module-ref %user-module
-                                (if (equal? cuirass? "cuirass")
-                                    'cuirass-jobs
-                                    'hydra-jobs))
-                    store `((guix
-                             . ((file-name . ,source)))))
-              (((names . thunks) ...)
-               (map (lambda (job thunk)
-                      (format (current-error-port) "evaluating '~a'... " job)
-                      (force-output (current-error-port))
-                      (cons job
-                            (assert-valid-job job
-                                              (call-with-time-display thunk))))
-                    names thunks)))
-            port))))))
+           (call-with-output-file output
+             (lambda (port)
+               ((module-ref %user-module 'cuirass-jobs)
+                store
+                `((guix-modular . ((file-name . ,source))))
+                (lambda args
+                  (write args port))))))))))
   ((command _ ...)
    (format (current-error-port) "Usage: ~a FILE [cuirass]
 Evaluate the Hydra or Cuirass jobs defined in FILE.~%"
@@ -128,4 +119,3 @@ Evaluate the Hydra or Cuirass jobs defined in FILE.~%"
 ;;; Local Variables:
 ;;; eval: (put 'call-with-time 'scheme-indent-function 1)
 ;;; End:
-
diff --git a/build-aux/cuirass/gnu-system.scm b/build-aux/cuirass/gnu-system.scm
index 0eb834cfba..71f33691fc 100644
--- a/build-aux/cuirass/gnu-system.scm
+++ b/build-aux/cuirass/gnu-system.scm
@@ -1,5 +1,8 @@
 ;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2020 Ludovic Courtès <[email-masked]>
 ;;; Copyright © 2017 Jan Nieuwenhuizen <[email-masked]>
+;;; Copyright © 2018, 2019 Clément Lassieur <[email-masked]>
+;;; Copyright © 2021 Mathieu Othacehe <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -21,5 +24,91 @@
 ;;; tool.
 ;;;
 
-(include "../hydra/gnu-system.scm")
-(include "hydra-to-cuirass.scm")
+(use-modules (guix inferior) (guix channels)
+             (guix)
+             (guix ui)
+             (srfi srfi-1)
+             (ice-9 match)
+             (ice-9 threads))
+
+;; XXX: Debugging hack: since `hydra-eval-guile-jobs' redirects the output
+;; port to the bit bucket, let us write to the error port instead.
+(setvbuf (current-error-port) 'line)
+(set-current-output-port (current-error-port))
+
+(define (find-current-checkout arguments)
+  "Find the first checkout of ARGUMENTS that provided the current file.
+Return #f if no such checkout is found."
+  (let ((current-root
+         (canonicalize-path
+          (string-append (dirname (current-filename)) "/../.."))))
+    (find (lambda (argument)
+            (and=> (assq-ref argument 'file-name)
+                   (lambda (name)
+                     (string=? name current-root)))) arguments)))
+
+(define* (cuirass-jobs store arguments register)
+  "Return a list of jobs where each job is a NAME/THUNK pair."
+
+  (define checkout
+    (find-current-checkout arguments))
+
+  (define commit
+    (assq-ref checkout 'revision))
+
+  (define source
+    (assq-ref checkout 'file-name))
+
+  (define instance
+    (checkout->channel-instance source #:commit commit))
+
+  (define derivation
+    ;; Compute the derivation of Guix for COMMIT.
+    (run-with-store store
+      (channel-instances->derivation (list instance))))
+
+  ;; TODO: Remove 'show-what-to-build' call when Cuirass' 'evaluate' scripts
+  ;; uses 'with-build-handler'.
+  (show-what-to-build store (list derivation))
+  (build-derivations store (list derivation))
+
+  ;; Open an inferior for the just-built Guix.
+  (call-with-temporary-directory
+   (lambda (directory)
+     (let* ((name (string-append directory "/ci-inferior"))
+            (socket (socket AF_UNIX SOCK_STREAM 0))
+            (inferior (open-inferior (derivation->output-path derivation))))
+
+       ;; XXX: The inferior cannot call directly the register procedure that
+       ;; is declared in Cuirass.  Use a socket to proxy the inferior
+       ;; registration requests.
+       (call-with-new-thread
+        (lambda ()
+          (bind socket AF_UNIX name)
+          (listen socket 1024)
+          (match (select (list socket) '() '() 60)
+            (((_) () ())
+             (match (accept socket)
+               ((client . address)
+                (setvbuf client 'block 1024)
+                (let loop ((exp (read client)))
+                  (unless (eof-object? exp)
+                    (apply register exp)
+                    (loop (read client)))))))
+            ((() () ())
+             #f))
+          (close-port socket)))
+
+       (inferior-eval '(use-modules (gnu ci) (ice-9 match)) inferior)
+       (inferior-eval-with-store
+        inferior store
+        `(lambda (store)
+           (let* ((socket (socket AF_UNIX SOCK_STREAM 0))
+                  (register (lambda args
+                              (write args socket))))
+             (connect socket AF_UNIX ,name)
+             (setvbuf socket 'block 1024)
+             (cuirass-jobs store '((superior-guix-checkout . ,checkout)
+                                   ,@arguments)
+                           register)
+             (close-port socket))))))))
diff --git a/build-aux/cuirass/guix-modular.scm b/build-aux/cuirass/guix-modular.scm
index cbbdbf1133..0b546e55df 100644
--- a/build-aux/cuirass/guix-modular.scm
+++ b/build-aux/cuirass/guix-modular.scm
@@ -1,6 +1,83 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017, 2018, 2020 Ludovic Courtès <[email-masked]>
+;;; Copyright © 2021 Mathieu Othacehe <[email-masked]>
 ;;;
-;;; This file defines Cuirass build jobs to build Guix itself.
+;;; This file is part of GNU Guix.
 ;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+;;;
+;;; This file defines a continuous integration job to build the same modular
+;;; Guix as 'guix pull', which is defined in (guix self).
+;;;
+
+(use-modules (guix store)
+             (guix config)
+             (guix utils)
+             ((guix packages) #:select (%hydra-supported-systems))
+             (guix derivations)
+             (guix monads)
+             (srfi srfi-1)
+             (ice-9 match))
+
+;; XXX: Debugging hack: since `hydra-eval-guile-jobs' redirects the output
+;; port to the bit bucket, let us write to the error port instead.
+(setvbuf (current-error-port) 'line)
+(set-current-output-port (current-error-port))
+
+(define* (build-job store register source version system)
+  "Register a Cuirass job a list building the modular Guix derivation from
+SOURCE for SYSTEM.  Use VERSION as the version identifier."
+  (define build
+    (primitive-load (string-append source "/build-aux/build-self.scm")))
+
+  (let ((name (string-append "guix." system))
+        (drv (run-with-store store
+               (build source #:version version #:system system
+                      #:pull-version 1
+                      #:guile-version "2.2"))))
+    (register name
+              #:derivation (derivation-file-name drv)
+              #:log (log-file store (derivation-file-name drv))
+              #:outputs (filter-map
+                         (lambda (res)
+                           (match res
+                             ((name . path)
+                              `(,name . ,path))))
+                         (derivation->output-paths drv))
+              #:nix-name (derivation-name drv)
+              #:system (derivation-system drv))))
+
+(define (cuirass-jobs store arguments register)
+  "Return Cuirass jobs."
+  (define systems
+    (match (assoc-ref arguments 'systems)
+      (#f              %hydra-supported-systems)
+      ((lst ...)       lst)
+      ((? string? str) (call-with-input-string str read))))
+
+  (define guix-checkout
+    (assq-ref arguments 'guix-modular))
+
+  (define version
+    (or (assq-ref guix-checkout 'revision)
+        "0.unknown"))
+
+  (let ((file (assq-ref guix-checkout 'file-name)))
+    (format (current-error-port) "using checkout ~s (~s; arguments: ~s)~%"
+            guix-checkout file arguments)
 
-(include "../hydra/guix-modular.scm")
-(include "hydra-to-cuirass.scm")
+    (for-each (lambda (system)
+                (build-job store register file version system))
+              systems)))
diff --git a/build-aux/cuirass/hydra-to-cuirass.scm b/build-aux/cuirass/hydra-to-cuirass.scm
deleted file mode 100644
index 75c77ea35a..0000000000
--- a/build-aux/cuirass/hydra-to-cuirass.scm
+++ /dev/null
@@ -1,47 +0,0 @@
-;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2017 Jan Nieuwenhuizen <[email-masked]>
-;;;
-;;; This file is part of GNU Guix.
-;;;
-;;; GNU Guix is free software; you can redistribute it and/or modify it
-;;; under the terms of the GNU General Public License as published by
-;;; the Free Software Foundation; either version 3 of the License, or (at
-;;; your option) any later version.
-;;;
-;;; GNU Guix is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-;;; GNU General Public License for more details.
-;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
-
-;;;
-;;; This file defines the conversion of Hydra build jobs to Cuirass build
-;;; jobs.  It is meant to be included in other files.
-;;;
-
-(use-modules ((guix licenses)
-              #:select (license? license-name license-uri license-comment)))
-
-(define (cuirass-jobs store arguments)
-  "Return Cuirass jobs."
-  (map hydra-job->cuirass-job (hydra-jobs store arguments)))
-
-(define (hydra-job->cuirass-job hydra-job)
-  (let ((name (car hydra-job))
-        (job ((cdr hydra-job))))
-    (lambda _ (acons #:job-name (symbol->string name)
-                     (map symbol-alist-entry->keyword-alist-entry job)))))
-
-(define (symbol-alist-entry->keyword-alist-entry entry)
-  (cons (symbol->keyword (car entry)) (entry->sexp-entry (cdr entry))))
-
-(define (entry->sexp-entry o)
-  (match o
-    ((? license?) `((name . (license-name o))
-                    (uri . ,(license-uri o))
-                    (comment . ,(license-comment o))))
-    ((lst ...)
-     (map entry->sexp-entry lst))
-    (_ o)))
diff --git a/build-aux/hydra/gnu-system.scm b/build-aux/hydra/gnu-system.scm
deleted file mode 100644
index a03324daeb..0000000000
--- a/build-aux/hydra/gnu-system.scm
+++ /dev/null
@@ -1,88 +0,0 @@
-;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2020 Ludovic Courtès <[email-masked]>
-;;; Copyright © 2017 Jan Nieuwenhuizen <[email-masked]>
-;;; Copyright © 2018, 2019 Clément Lassieur <[email-masked]>
-;;;
-;;; This file is part of GNU Guix.
-;;;
-;;; GNU Guix is free software; you can redistribute it and/or modify it
-;;; under the terms of the GNU General Public License as published by
-;;; the Free Software Foundation; either version 3 of the License, or (at
-;;; your option) any later version.
-;;;
-;;; GNU Guix is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-;;; GNU General Public License for more details.
-;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
-
-;;;
-;;; This file defines build jobs for the Hydra continuation integration
-;;; tool.
-;;;
-
-(use-modules (guix inferior) (guix channels)
-             (guix)
-             (guix ui)
-             (srfi srfi-1)
-             (ice-9 match))
-
-;; XXX: Debugging hack: since `hydra-eval-guile-jobs' redirects the output
-;; port to the bit bucket, let us write to the error port instead.
-(setvbuf (current-error-port) 'line)
-(set-current-output-port (current-error-port))
-
-(define (find-current-checkout arguments)
-  "Find the first checkout of ARGUMENTS that provided the current file.
-Return #f if no such checkout is found."
-  (let ((current-root
-         (canonicalize-path
-          (string-append (dirname (current-filename)) "/../.."))))
-    (find (lambda (argument)
-            (and=> (assq-ref argument 'file-name)
-                   (lambda (name)
-                     (string=? name current-root)))) arguments)))
-
-(define (hydra-jobs store arguments)
-  "Return a list of jobs where each job is a NAME/THUNK pair."
-
-  (define checkout
-    (find-current-checkout arguments))
-
-  (define commit
-    (assq-ref checkout 'revision))
-
-  (define source
-    (assq-ref checkout 'file-name))
-
-  (define instance
-    (checkout->channel-instance source #:commit commit))
-
-  (define derivation
-    ;; Compute the derivation of Guix for COMMIT.
-    (run-with-store store
-      (channel-instances->derivation (list instance))))
-
-  ;; TODO: Remove 'show-what-to-build' call when Cuirass' 'evaluate' scripts
-  ;; uses 'with-build-handler'.
-  (show-what-to-build store (list derivation))
-  (build-derivations store (list derivation))
-
-  ;; Open an inferior for the just-built Guix.
-  (let ((inferior (open-inferior (derivation->output-path derivation))))
-    (inferior-eval '(use-modules (gnu ci) (ice-9 match)) inferior)
-
-    (map (match-lambda
-           ((name . fields)
-            ;; Hydra expects a thunk, so here it is.
-            (cons name (lambda () fields))))
-         (inferior-eval-with-store
-          inferior store
-          `(lambda (store)
-             (map (match-lambda
-                    ((name . thunk)
-                     (cons name (thunk))))
-                  (hydra-jobs store '((superior-guix-checkout . ,checkout)
-                                      ,@arguments))))))))
diff --git a/build-aux/hydra/guix-modular.scm b/build-aux/hydra/guix-modular.scm
deleted file mode 100644
index 060b84b8ef..0000000000
--- a/build-aux/hydra/guix-modular.scm
+++ /dev/null
@@ -1,91 +0,0 @@
-;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2017, 2018, 2020 Ludovic Courtès <[email-masked]>
-;;;
-;;; This file is part of GNU Guix.
-;;;
-;;; GNU Guix is free software; you can redistribute it and/or modify it
-;;; under the terms of the GNU General Public License as published by
-;;; the Free Software Foundation; either version 3 of the License, or (at
-;;; your option) any later version.
-;;;
-;;; GNU Guix is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-;;; GNU General Public License for more details.
-;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
-
-;;;
-;;; This file defines a continuous integration job to build the same modular
-;;; Guix as 'guix pull', which is defined in (guix self).
-;;;
-
-(use-modules (guix store)
-             (guix config)
-             (guix utils)
-             ((guix packages) #:select (%hydra-supported-systems))
-             (guix derivations)
-             (guix monads)
-             ((guix licenses) #:prefix license:)
-             (srfi srfi-1)
-             (ice-9 match))
-
-;; XXX: Debugging hack: since `hydra-eval-guile-jobs' redirects the output
-;; port to the bit bucket, let us write to the error port instead.
-(setvbuf (current-error-port) 'line)
-(set-current-output-port (current-error-port))
-
-(define* (build-job store source version system)
-  "Return a Hydra job a list building the modular Guix derivation from SOURCE
-for SYSTEM.  Use VERSION as the version identifier."
-  (lambda ()
-    (define build
-      (primitive-load (string-append source "/build-aux/build-self.scm")))
-
-    (let ((drv (run-with-store store
-                 (build source #:version version #:system system
-                        #:pull-version 1
-                        #:guile-version "2.2"))))
-      `((derivation . ,(derivation-file-name drv)) ;the latest 2.2.x
-        (log . ,(log-file store (derivation-file-name drv)))
-        (outputs . ,(filter-map (lambda (res)
-                                  (match res
-                                    ((name . path)
-                                     `(,name . ,path))))
-                                (derivation->output-paths drv)))
-        (nix-name . ,(derivation-name drv))
-        (system . ,(derivation-system drv))
-        (description . "Modular Guix")
-        (long-description
-         . "This is the modular Guix package as produced by 'guix pull'.")
-        (license . ,license:gpl3+)
-        (home-page . ,%guix-home-page-url)
-        (maintainers . (,%guix-bug-report-address))))))
-
-(define (hydra-jobs store arguments)
-  "Return Hydra jobs."
-  (define systems
-    (match (assoc-ref arguments 'systems)
-      (#f              %hydra-supported-systems)
-      ((lst ...)       lst)
-      ((? string? str) (call-with-input-string str read))))
-
-  (define guix-checkout
-    (or (assq-ref arguments 'guix)                ;Hydra on hydra
-        (assq-ref arguments 'guix-modular)))      ;Cuirass on berlin
-
-  (define version
-    (or (assq-ref guix-checkout 'revision)
-        "0.unknown"))
-
-  (let ((file (assq-ref guix-checkout 'file-name)))
-    (format (current-error-port) "using checkout ~s (~s; arguments: ~s)~%"
-            guix-checkout file arguments)
-
-    (map (lambda (system)
-           (let ((name (string->symbol
-                        (string-append "guix." system))))
-             `(,name
-               . ,(build-job store file version system))))
-         systems)))
diff --git a/build-aux/hydra/guix.scm b/build-aux/hydra/guix.scm
deleted file mode 100644
index 08193ec82e..0000000000
--- a/build-aux/hydra/guix.scm
+++ /dev/null
@@ -1,106 +0,0 @@
-;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <[email-masked]>
-;;;
-;;; This file is part of GNU Guix.
-;;;
-;;; GNU Guix is free software; you can redistribute it and/or modify it
-;;; under the terms of the GNU General Public License as published by
-;;; the Free Software Foundation; either version 3 of the License, or (at
-;;; your option) any later version.
-;;;
-;;; GNU Guix is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-;;; GNU General Public License for more details.
-;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
-
-;;;
-;;; This file defines build jobs of Guix itself for the Hydra continuation
-;;; integration tool.
-;;;
-
-;; Attempt to use our very own Guix modules.
-(eval-when (expand load eval)
-
-  ;; Ignore any available .go, and force recompilation.  This is because our
-  ;; checkout in the store has mtime set to the epoch, and thus .go files look
-  ;; newer, even though they may not correspond.
-  (set! %fresh-auto-compile #t)
-
-  ;; Display which files are loaded.
-  (set! %load-verbosely #t)
-
-  (and=> (assoc-ref (current-source-location) 'filename)
-         (lambda (file)
-           (let ((dir (string-append (dirname file) "/../..")))
-             (format (current-error-port) "prepending ~s to the load path~%"
-                     dir)
-             (set! %load-path (cons dir %load-path))))))
-
-
-(use-modules (guix store)
-             (guix packages)
-             (guix utils)
-             (guix grafts)
-             (guix derivations)
-             (guix build-system gnu)
-             (gnu packages package-management)
-             (srfi srfi-1)
-             (srfi srfi-26)
-             (ice-9 match))
-
-;; XXX: Debugging hack: since `hydra-eval-guile-jobs' redirects the output
-;; port to the bit bucket, let us write to the error port instead.
-(setvbuf (current-error-port) _IOLBF)
-(set-current-output-port (current-error-port))
-
-(define* (package->alist store package system
-                         #:optional (package-derivation package-derivation))
-  "Convert PACKAGE to an alist suitable for Hydra."
-  `((derivation . ,(derivation-file-name
-                    (parameterize ((%graft? #f))
-                      (package-derivation store package system
-                                          #:graft? #f))))
-    (description . ,(package-synopsis package))
-    (long-description . ,(package-description package))
-    (license . ,(package-license package))
-    (home-page . ,(package-home-page package))
-    (maintainers . ("[email-masked]"))))
-
-(define (hydra-jobs store arguments)
-  "Return Hydra jobs."
-  (define systems
-    (match (filter-map (match-lambda
-                        (('system . value)
-                         value)
-                        (_ #f))
-                       arguments)
-      ((lst ..1)
-       lst)
-      (_
-       (list (%current-system)))))
-
-  (define guix-checkout
-    (assq-ref arguments 'guix))
-
-  (let ((file (assq-ref guix-checkout 'file-name)))
-    (format (current-error-port) "using checkout ~s (~s)~%"
-            guix-checkout file)
-
-    `((tarball . ,(cute package->alist store
-                        (dist-package guix file)
-                        (%current-system)))
-
-      ,@(map (lambda (system)
-               (let ((name (string->symbol
-                            (string-append "guix." system))))
-                 `(,name
-                   . ,(cute package->alist store
-                            (package
-                              (inherit guix)
-                              (version "latest")
-                              (source file))
-                            system))))
-             %hydra-supported-systems))))
diff --git a/gnu/ci.scm b/gnu/ci.scm
index 96bff64875..80c1553916 100644
--- a/gnu/ci.scm
+++ b/gnu/ci.scm
@@ -3,7 +3,7 @@
 ;;; Copyright © 2017, 2020 Jan (janneke) Nieuwenhuizen <[email-masked]>
 ;;; Copyright © 2018, 2019 Clément Lassieur <[email-masked]>
 ;;; Copyright © 2020 Julien Lepiller <[email-masked]>
-;;; Copyright © 2020 Mathieu Othacehe <[email-masked]>
+;;; Copyright © 2020, 2021 Mathieu Othacehe <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -64,67 +64,70 @@
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
   #:use-module (ice-9 match)
-  #:export (%cross-targets
+  #:export (%core-packages
+            %cross-targets
             channel-source->package
-            hydra-jobs))
+            cuirass-jobs))
 
 ;;; Commentary:
 ;;;
-;;; This file defines build jobs for the Hydra and Cuirass continuation
-;;; integration tools.
+;;; This file defines build jobs for Cuirass.
 ;;;
 ;;; Code:
 
-(define* (package->alist store package system
-                         #:optional (package-derivation package-derivation))
-  "Convert PACKAGE to an alist suitable for Hydra."
-  (parameterize ((%graft? #f))
-    (let ((drv (package-derivation store package system
-                                   #:graft? #f)))
-      `((derivation . ,(derivation-file-name drv))
-        (log . ,(log-file store (derivation-file-name drv)))
-        (outputs . ,(filter-map (lambda (res)
-                                  (match res
-                                    ((name . path)
-                                     `(,name . ,path))))
-                                (derivation->output-paths drv)))
-        (nix-name . ,(derivation-name drv))
-        (system . ,(derivation-system drv))
-        (description . ,(package-synopsis package))
-        (long-description . ,(package-description package))
-
-        ;; XXX: Hydra ignores licenses that are not a <license> structure or a
-        ;; list thereof.
-        (license . ,(let loop ((license (package-license package)))
-                      (match license
-                        ((? license?)
-                         (license-name license))
-                        ((lst ...)
-                         (map loop license)))))
-
-        (home-page . ,(package-home-page package))
-        (maintainers . ("[email-masked]"))
-        (max-silent-time . ,(or (assoc-ref (package-properties package)
-                                           'max-silent-time)
-                                3600))              ;1 hour by default
-        (timeout . ,(or (assoc-ref (package-properties package) 'timeout)
-                        72000))))))                  ;20 hours by default
-
-(define (package-job store job-name package system)
-  "Return a job called JOB-NAME that builds PACKAGE on SYSTEM."
-  (let ((job-name (symbol-append job-name (string->symbol ".")
-                                 (string->symbol system))))
-    `(,job-name . ,(cut package->alist store package system))))
-
-(define (package-cross-job store job-name package target system)
-  "Return a job called TARGET.JOB-NAME that cross-builds PACKAGE for TARGET on
-SYSTEM."
-  `(,(symbol-append (string->symbol target) (string->symbol ".") job-name
-                    (string->symbol ".") (string->symbol system)) .
-    ,(cute package->alist store package system
-           (lambda* (store package system #:key graft?)
-             (package-cross-derivation store package target system
-                                       #:graft? graft?)))))
+(define* (register-job-from-drv store drv
+                                #:key
+                                name
+                                register
+                                period
+                                (max-silent-time 3600)
+                                (timeout 3600))
+  "Register DRV in Cuirass by calling the REGISTER procedure."
+  ;; See "register-job" procedure in the (cuirass jobs) module.
+  (register name
+            #:derivation (derivation-file-name drv)
+            #:log (log-file store (derivation-file-name drv))
+            #:outputs (filter-map
+                       (lambda (res)
+                         (match res
+                           ((name . path)
+                            `(,name . ,path))))
+                       (derivation->output-paths drv))
+            #:nix-name (derivation-name drv)
+            #:system (derivation-system drv)
+            #:period period
+            #:max-silent-time max-silent-time
+            #:timeout timeout))
+
+(define* (package-job store job-name register package system
+                      #:key cross? target)
+  "Register a job called JOB-NAME that builds PACKAGE on SYSTEM."
+  (let ((job-name (string-append job-name "." system)))
+    (parameterize ((%graft? #f))
+      (let* ((drv (if cross?
+                      (package-cross-derivation store package target system
+                                                #:graft? #f)
+                      (package-derivation store package system
+                                          #:graft? #f)))
+             (max-silent-time (or (assoc-ref (package-properties package)
+                                             'max-silent-time)
+                                  3600))
+             (timeout (or (assoc-ref (package-properties package)
+                                     'timeout)
+                          72000)))
+        (register-job-from-drv store drv
+                               #:name job-name
+                               #:register register
+                               #:max-silent-time max-silent-time
+                               #:timeout timeout)))))
+
+(define (package-cross-job store job-name register package target system)
+  "Register a job called TARGET.JOB-NAME that cross-builds PACKAGE for TARGET
+on SYSTEM."
+  (let ((name (string-append target "." job-name "." system)))
+    (package-job store name register package system
+                 #:cross? #t
+                 #:target target)))
 
 (define %core-packages
   ;; Note: Don't put the '-final' package variants because (1) that's
@@ -157,8 +160,8 @@ SYSTEM."
     "i686-w64-mingw32"
     "x86_64-w64-mingw32"))
 
-(define (cross-jobs store system)
-  "Return a list of cross-compilation jobs for SYSTEM."
+(define (cross-jobs store register system)
+  "Register a list of cross-compilation jobs for SYSTEM."
   (define (from-32-to-64? target)
     ;; Return true if SYSTEM is 32-bit and TARGET is 64-bit.  This hack
     ;; prevents known-to-fail cross-builds from i686-linux or armhf-linux to
@@ -192,13 +195,14 @@ SYSTEM."
     (lambda (x)
       (or (proc1 x) (proc2 x) (proc3 x))))
 
-  (append-map (lambda (target)
-                (map (lambda (package)
-                       (package-cross-job store (job-name package)
-                                          package target system))
-                     (packages-to-cross-build target)))
-              (remove (either from-32-to-64? same? pointless?)
-                      %cross-targets)))
+  (for-each (lambda (target)
+              (for-each (lambda (package)
+                          (package-cross-job store (job-name package)
+                                             register package
+                                             target system))
+                        (packages-to-cross-build target)))
+            (remove (either from-32-to-64? same? pointless?)
+                    %cross-targets)))
 
 ;; Architectures that are able to build or cross-build Guix System images.
 ;; This does not mean that other architectures are not supported, only that
@@ -215,36 +219,17 @@ SYSTEM."
 (define (hours hours)
   (* 3600 hours))
 
-(define (image-jobs store system)
+(define (image-jobs store register system)
   "Return a list of jobs that build images for SYSTEM.  Those jobs are
 expensive in storage and I/O operations, hence their periodicity is limited by
 passing the PERIOD argument."
-  (define (->alist drv)
-    `((derivation . ,(derivation-file-name drv))
-      (log . ,(log-file store (derivation-file-name drv)))
-      (outputs . ,(filter-map (lambda (res)
-                                (match res
-                                  ((name . path)
-                                   `(,name . ,path))))
-                              (derivation->output-paths drv)))
-      (nix-name . ,(derivation-name drv))
-      (system . ,(derivation-system drv))
-      (description . "Stand-alone image of the GNU system")
-      (long-description . "This is a demo stand-alone image of the GNU
-system.")
-      (license . ,(license-name gpl3+))
-      (period . ,(hours 48))
-      (max-silent-time . 3600)
-      (timeout . 3600)
-      (home-page . ,%guix-home-page-url)
-      (maintainers . ("[email-masked]"))))
-
   (define (->job name drv)
-    (let ((name (symbol-append name (string->symbol ".")
-                               (string->symbol system))))
-      `(,name . ,(lambda ()
-                   (parameterize ((%graft? #f))
-                     (->alist drv))))))
+    (let ((name (string-append name "." system)))
+      (parameterize ((%graft? #f))
+        (register-job-from-drv store drv
+                               #:name name
+                               #:register register
+                               #:period (hours 48)))))
 
   (define (build-image image)
     (run-with-store store
@@ -256,25 +241,26 @@ system.")
     (expt 2 20))
 
   (if (member system %guix-system-supported-systems)
-      `(,(->job 'usb-image
+      `(,(->job "usb-image"
                 (build-image
                  (image
                   (inherit efi-disk-image)
                   (operating-system installation-os))))
-        ,(->job 'iso9660-image
+        ,(->job "iso9660-image"
                 (build-image
                  (image
                   (inherit (image-with-label
-                             iso9660-image
-                             (string-append "GUIX_" system "_"
-                                            (if (> (string-length %guix-version) 7)
-                                                (substring %guix-version 0 7)
-                                                %guix-version))))
+                            iso9660-image
+                            (string-append "GUIX_" system "_"
+                                           (if (> (string-length %guix-version) 7)
+                                               (substring %guix-version 0 7)
+                                               %guix-version))))
                   (operating-system installation-os))))
         ;; Only cross-compile Guix System images from x86_64-linux for now.
         ,@(if (string=? system "x86_64-linux")
               (map (lambda (image)
-                     (->job (image-name image) (build-image image)))
+                     (->job (symbol->string (image-name image))
+                            (build-image image)))
                    %guix-system-images)
               '()))
       '()))
@@ -319,122 +305,85 @@ system.")
     (native-inputs '())
     (propagated-inputs '())))
 
-(define* (system-test-jobs store system
+(define* (system-test-jobs store register system
                            #:key source commit)
-  "Return a list of jobs for the system tests."
-  (define (test->thunk test)
-    (lambda ()
-      (define drv
-        (run-with-store store
-          (mbegin %store-monad
-            (set-current-system system)
-            (set-grafting #f)
-            (set-guile-for-build (default-guile))
-            (system-test-value test))))
-
-      ;; Those tests are extremely expensive in I/O operations and storage
-      ;; size, use the "period" attribute to run them with a period of at
-      ;; least 48 hours.
-      `((derivation . ,(derivation-file-name drv))
-        (log . ,(log-file store (derivation-file-name drv)))
-        (outputs . ,(filter-map (lambda (res)
-                                  (match res
-                                    ((name . path)
-                                     `(,name . ,path))))
-                                (derivation->output-paths drv)))
-        (nix-name . ,(derivation-name drv))
-        (system . ,(derivation-system drv))
-        (description . ,(format #f "Guix '~a' system test"
-                                (system-test-name test)))
-        (long-description . ,(system-test-description test))
-        (license . ,(license-name gpl3+))
-        (period . ,(hours 48))
-        (max-silent-time . 3600)
-        (timeout . 3600)
-        (home-page . ,%guix-home-page-url)
-        (maintainers . ("[email-masked]")))))
-
+  "Register a list of jobs for the system tests."
   (define (->job test)
-    (let ((name (string->symbol
-                 (string-append "test." (system-test-name test)
-                                "." system))))
-      (cons name (test->thunk test))))
+    (parameterize ((current-guix-package
+                    (channel-source->package source #:commit commit)))
+      (let ((name (string-append "test." (system-test-name test)
+                                 "." system))
+            (drv (run-with-store store
+                   (mbegin %store-monad
+                     (set-current-system system)
+                     (set-grafting #f)
+                     (set-guile-for-build (default-guile))
+                     (system-test-value test)))))
+
+        ;; Those tests are extremely expensive in I/O operations and storage
+        ;; size, use the "period" attribute to run them with a period of at
+        ;; least 48 hours.
+        (register-job-from-drv store drv
+                               #:name name
+                               #:register register
+                               #:period (hours 24)))))
 
   (if (member system %guix-system-supported-systems)
       ;; Override the value of 'current-guix' used by system tests.  Using a
       ;; channel instance makes tests that rely on 'current-guix' less
       ;; expensive.  It also makes sure we get a valid Guix package when this
       ;; code is not running from a checkout.
-      (parameterize ((current-guix-package
-                      (channel-source->package source #:commit commit)))
-        (map ->job (all-system-tests)))
+      (for-each ->job (all-system-tests))
       '()))
 
-(define (tarball-jobs store system)
-  "Return Hydra jobs to build the self-contained Guix binary tarball."
-  (define (->alist drv)
-    `((derivation . ,(derivation-file-name drv))
-      (log . ,(log-file store (derivation-file-name drv)))
-      (outputs . ,(filter-map (lambda (res)
-                                (match res
-                                  ((name . path)
-                                   `(,name . ,path))))
-                              (derivation->output-paths drv)))
-      (nix-name . ,(derivation-name drv))
-      (system . ,(derivation-system drv))
-      (description . "Stand-alone binary Guix tarball")
-      (long-description . "This is a tarball containing binaries of Guix and
-all its dependencies, and ready to be installed on \"foreign\" distributions.")
-      (license . ,(license-name gpl3+))
-      (home-page . ,%guix-home-page-url)
-      (maintainers . ("[email-masked]"))
-      (period . ,(hours 24))))
-
+(define (tarball-jobs store register system)
+  "Register jobs to build the self-contained Guix binary tarball."
   (define (->job name drv)
-    (let ((name (symbol-append name (string->symbol ".")
-                               (string->symbol system))))
-      `(,name . ,(lambda ()
-                   (parameterize ((%graft? #f))
-                     (->alist drv))))))
+    (let ((name (string-append name "." system)))
+      (parameterize ((%graft? #f))
+        (register-job-from-drv store drv
+                               #:name name
+                               #:register register
+                               #:period (hours 24)))))
 
   ;; XXX: Add a job for the stable Guix?
-  (list (->job 'binary-tarball
-               (run-with-store store
-                 (mbegin %store-monad
-                   (set-guile-for-build (default-guile))
-                   (>>= (profile-derivation (packages->manifest (list guix)))
-                        (lambda (profile)
-                          (self-contained-tarball "guix-binary" profile
-                                                  #:localstatedir? #t
-                                                  #:compressor
-                                                  (lookup-compressor "xz")))))
-                 #:system system))))
+  (->job "binary-tarball"
+         (run-with-store store
+           (mbegin %store-monad
+             (set-guile-for-build (default-guile))
+             (>>= (profile-derivation (packages->manifest (list guix)))
+                  (lambda (profile)
+                    (self-contained-tarball "guix-binary" profile
+                                            #:localstatedir? #t
+                                            #:compressor
+                                            (lookup-compressor "xz")))))
+           #:system system)))
 
 (define job-name
   ;; Return the name of a package's job.
-  (compose string->symbol package-name))
+  package-name)
 
 (define package->job
   (let ((base-packages
          (delete-duplicates
           (append-map (match-lambda
-                       ((_ package _ ...)
-                        (match (package-transitive-inputs package)
-                          (((_ inputs _ ...) ...)
-                           inputs))))
+                        ((_ package _ ...)
+                         (match (package-transitive-inputs package)
+                           (((_ inputs _ ...) ...)
+                            inputs))))
                       (%final-inputs)))))
-    (lambda (store package system)
+    (lambda (store register package system)
       "Return a job for PACKAGE on SYSTEM, or #f if this combination is not
 valid."
       (cond ((member package base-packages)
-             (package-job store (symbol-append 'base. (job-name package))
-                          package system))
+             (package-job store (string-append "base." (job-name package))
+                          register package system))
             ((supported-package? package system)
              (let ((drv (package-derivation store package system
                                             #:graft? #f)))
                (and (substitutable-derivation? drv)
                     (package-job store (job-name package)
-                                 package system))))
+                                 register package system))))
             (else
              #f)))))
 
@@ -497,11 +446,11 @@ Return #f if no such checkout is found."
 
 
 ;;;
-;;; Hydra entry point.
+;;; Cuirass entry point.
 ;;;
 
-(define (hydra-jobs store arguments)
-  "Return Hydra jobs."
+(define (cuirass-jobs store arguments register)
+  "Register Cuirass jobs."
   (define subset
     (match (assoc-ref arguments 'subset)
       ("core" 'core)                              ; only build core packages
@@ -529,55 +478,57 @@ Return #f if no such checkout is found."
   ;; Turn off grafts.  Grafting is meant to happen on the user's machines.
   (parameterize ((%graft? #f))
     ;; Return one job for each package, except bootstrap packages.
-    (append-map (lambda (system)
-                  (format (current-error-port)
-                          "evaluating for '~a' (heap size: ~a MiB)...~%"
-                          system
-                          (round
-                           (/ (assoc-ref (gc-stats) 'heap-size)
-                              (expt 2. 20))))
-                  (invalidate-derivation-caches!)
-                  (case subset
-                    ((all)
-                     ;; Build everything, including replacements.
-                     (let ((all (all-packages))
-                           (job (lambda (package)
-                                  (package->job store package
-                                                system))))
-                       (append (filter-map job all)
-                               (image-jobs store system)
-                               (system-test-jobs store system
-                                                 #:source source
-                                                 #:commit commit)
-                               (tarball-jobs store system)
-                               (cross-jobs store system))))
-                    ((core)
-                     ;; Build core packages only.
-                     (append (map (lambda (package)
-                                    (package-job store (job-name package)
-                                                 package system))
-                                  %core-packages)
-                             (cross-jobs store system)))
-                    ((hello)
-                     ;; Build hello package only.
-                     (let ((hello (specification->package "hello")))
-                       (list (package-job store (job-name hello) hello system))))
-                    ((list)
-                     ;; Build selected list of packages only.
-                     (let* ((names (assoc-ref arguments 'subset))
-                            (packages (map specification->package names)))
-                       (map (lambda (package)
-                              (package-job store (job-name package)
-                                           package system))
-                            packages)))
-                    ((manifests)
-                     ;; Build packages in the list of manifests.
-                     (let* ((manifests (arguments->manifests arguments))
-                            (packages (manifests->packages store manifests)))
-                       (map (lambda (package)
-                              (package-job store (job-name package)
-                                           package system))
-                            packages)))
-                    (else
-                     (error "unknown subset" subset))))
-                systems)))
+    (for-each (lambda (system)
+                (format (current-error-port)
+                        "evaluating for '~a' (heap size: ~a MiB)...~%"
+                        system
+                        (round
+                         (/ (assoc-ref (gc-stats) 'heap-size)
+                            (expt 2. 20))))
+                (invalidate-derivation-caches!)
+                (case subset
+                  ((all)
+                   ;; Build everything, including replacements.
+                   (let ((all (all-packages))
+                         (job (lambda (package)
+                                (package->job store register
+                                              package system))))
+                     (filter-map job all)
+                     (image-jobs store register system)
+                     (system-test-jobs store register system
+                                       #:source source
+                                       #:commit commit)
+                     (tarball-jobs store register system)
+                     (cross-jobs store register system)))
+                  ((core)
+                   ;; Build core packages only.
+                   (begin
+                     (for-each (lambda (package)
+                                 (package-job store (job-name package)
+                                              register package system))
+                               %core-packages)
+                     (cross-jobs store register system)))
+                  ((hello)
+                   ;; Build hello package only.
+                   (let ((hello (specification->package "hello")))
+                     (list (package-job store (job-name hello)
+                                        register hello system))))
+                  ((list)
+                   ;; Build selected list of packages only.
+                   (let* ((names (assoc-ref arguments 'subset))
+                          (packages (map specification->package names)))
+                     (for-each (lambda (package)
+                                 (package-job store (job-name package)
+                                              register package system))
+                               packages)))
+                  ((manifests)
+                   ;; Build packages in the list of manifests.
+                   (let* ((manifests (arguments->manifests arguments))
+                          (packages (manifests->packages store manifests)))
+                     (for-each (lambda (package)
+                                 (package-job store (job-name package)
+                                              register package system))
+                               packages)))
+                  (else
+                   (error "unknown subset" subset))))
+              systems)))
-- 
2.24.0