channels: Record 'guix' channel metadata in (guix config).

Partially fixes <https://bugs.gnu.org/45896>.

* guix/config.scm.in (%channel-metadata): New variable.
* guix/describe.scm (channel-metadata): Use it.
(current-channels): New procedure.
(current-profile-entries): Clarify docstring.
* guix/self.scm (compiled-guix): Add #:channel-metadata and pass it to
'make-config.scm'.
(make-config.scm): Add #:channel-metadata and define '%channel-metadata'
in the generated file.
(guix-derivation): Add #:channel-metadata and pass it to 'compiled-guix'.
* guix/channels.scm (build-from-source): Replace 'name', 'source', and
'commit' parameters with 'instance'.  Pass #:channel-metadata to BUILD.
(build-channel-instance): Adjust accordingly.
* build-aux/build-self.scm (build-program): Add #:channel-metadata
and pass it to 'guix-derivation'.
(build): Add #:channel-metadata and pass it to 'build-program'.
* guix/scripts/describe.scm (display-profile-info): Add optional
'channels' parameter.  Pass it to 'display-profile-content'.
(display-profile-content): Add optional 'channels' parameter and honor
it.  Iterate on CHANNELS rather than on the manifest entries of
PROFILE.
(guix-describe): When PROFILE is #f, call 'current-channels' and pass it
to 'display-profile-info', unless it returns the empty list.

1 files changed, 8 insertions, 3 deletions

diff --git a/build-aux/build-self.scm b/build-aux/build-self.scm
index d5bc5fb46e..6a3b9c83d4 100644
--- a/build-aux/build-self.scm
+++ b/build-aux/build-self.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2014, 2016, 2017, 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2014, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -241,7 +241,7 @@ interface (FFI) of Guile.")
 
 (define* (build-program source version
                         #:optional (guile-version (effective-version))
-                        #:key (pull-version 0))
+                        #:key (pull-version 0) (channel-metadata #f))
   "Return a program that computes the derivation to build Guix from SOURCE."
   (define select?
     ;; Select every module but (guix config) and non-Guix modules.
@@ -359,6 +359,8 @@ interface (FFI) of Guile.")
                              (run-with-store store
                                (guix-derivation source version
                                                 #$guile-version
+                                                #:channel-metadata
+                                                '#$channel-metadata
                                                 #:pull-version
                                                 #$pull-version)
                                #:system system)
@@ -380,7 +382,9 @@ interface (FFI) of Guile.")
 
 ;; The procedure below is our return value.
 (define* (build source
-                #:key verbose? (version (date-version-string)) system
+                #:key verbose?
+                (version (date-version-string)) channel-metadata
+                system
                 (pull-version 0)
 
                 ;; For the standalone Guix, default to Guile 3.0.  For old
@@ -397,6 +401,7 @@ files."
   ;; Build the build program and then use it as a trampoline to build from
   ;; SOURCE.
   (mlet %store-monad ((build  (build-program source version guile-version
+                                             #:channel-metadata channel-metadata
                                              #:pull-version pull-version))
                       (system (if system (return system) (current-system)))
                       (home -> (getenv "HOME"))