build-system: Add 'channel-build-system'.

* gnu/ci.scm (channel-build-system, channel-source->package): Remove.
* gnu/packages/package-management.scm (channel-source->package): New
procedure, moved from (gnu ci).
* guix/build-system/channel.scm: New file, with code moved from (gnu ci).
* doc/guix.texi (Build Systems): Document it.

1 files changed, 58 insertions, 0 deletions

diff --git a/guix/build-system/channel.scm b/guix/build-system/channel.scm
new file mode 100644
index 0000000000..227eb08373
--- /dev/null
+++ b/guix/build-system/channel.scm
@@ -0,0 +1,58 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2019-2021 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; 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/>.
+
+(define-module (guix build-system channel)
+  #:use-module ((guix store) #:select (%store-monad))
+  #:use-module ((guix gexp) #:select (lower-object))
+  #:use-module (guix monads)
+  #:use-module (guix channels)
+  #:use-module (guix build-system)
+  #:export (channel-build-system))
+
+;;; Commentary:
+;;;
+;;; The "channel" build system lets you build Guix instances from channel
+;;; specifications, similar to how 'guix time-machine' would do it, as regular
+;;; packages.
+;;;
+;;; Code:
+
+(define channel-build-system
+  ;; Build system used to "convert" a channel instance to a package.
+  (let* ((build (lambda* (name inputs
+                               #:key source commit system
+                               #:allow-other-keys)
+                  (mlet* %store-monad ((source (if (string? source)
+                                                   (return source)
+                                                   (lower-object source)))
+                                       (instance
+                                        -> (checkout->channel-instance
+                                            source #:commit commit)))
+                    (channel-instances->derivation (list instance)))))
+         (lower (lambda* (name #:key system source commit
+                               #:allow-other-keys)
+                  (bag
+                    (name name)
+                    (system system)
+                    (build build)
+                    (arguments `(#:source ,source
+                                 #:commit ,commit))))))
+    (build-system (name 'channel)
+                  (description "Turn a channel instance into a package.")
+                  (lower lower))))
+