GNU bug report logs - #45896
Non-pull ‘guix’ should know its channels

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: <bug-guix <at> gnu.org>
Subject: Non-pull ‘guix’ should know its channels
Date: Fri, 15 Jan 2021 18:51:14 +0100

Related to <https://issues.guix.gnu.org/45895>, we have the problem that
the ‘guix’ command coming from the ‘guix’ package doesn’t know its
provenance: ‘guix describe’ errors out.

We should fix it by storing a meta-data file within the ‘guix’ package.

Likewise, on foreign distros, /usr/local/bin/guix may point to a ‘guix
pull’-guix, but because of the symlink, ‘guix describe’ won’t work:

--8<---------------cut here---------------start------------->8---
$ type -P guix
/home/ludo/.config/guix/current/bin/guix
$ guix describe
Generacio 171	Jan 11 2021 11:38:39	(nuna)
  guix 458cb25
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 458cb25b9e7e7c954f468023abea2bebb5d8c75b
$ ln -s $(type -P guix) /tmp
$ /tmp/guix describe
guix describe: error: failed to determine origin
hint: Perhaps this `guix' command was not obtained with `guix pull'? Its
version string is 458cb25b9e7e7c954f468023abea2bebb5d8c75b.
--8<---------------cut here---------------end--------------->8---

We should probably store proper provenance info directly in the ‘guix’
output, just like we store the commit ID in (guix config).

Ludo’.

Message #12 received at 45896 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: 45896 <at> debbugs.gnu.org
Subject: Re: bug#45896: Non-pull ‘guix’ should know
 its channels
Date: Tue, 26 Jan 2021 14:16:57 +0100

Ludovic Courtès <ludo <at> gnu.org> skribis:

> Likewise, on foreign distros, /usr/local/bin/guix may point to a ‘guix
> pull’-guix, but because of the symlink, ‘guix describe’ won’t work:
>
> $ type -P guix
> /home/ludo/.config/guix/current/bin/guix
> $ guix describe
> Generacio 171	Jan 11 2021 11:38:39	(nuna)
>   guix 458cb25
>     repository URL: https://git.savannah.gnu.org/git/guix.git
>     branch: master
>     commit: 458cb25b9e7e7c954f468023abea2bebb5d8c75b
> $ ln -s $(type -P guix) /tmp
> $ /tmp/guix describe
> guix describe: error: failed to determine origin
> hint: Perhaps this `guix' command was not obtained with `guix pull'? Its
> version string is 458cb25b9e7e7c954f468023abea2bebb5d8c75b.

This problem extends beyond that: channel modules are not found if the
symlink is dereferenced:

--8<---------------cut here---------------start------------->8---
$ /tmp/guix-science/bin/guix describe 
Generacio 1     Jan 26 2021 14:13:46    (nuna)
  guix-past 829923f
    repository URL: https://gitlab.inria.fr/guix-hpc/guix-past
    branch: master
    commit: 829923f01f894f1e687735627025ada26230832f
  guix-science cf87b05
    repository URL: https://github.com/guix-science/guix-science.git
    branch: master
    commit: cf87b0501c4a38b96edf41025a27bf1cb91f521a
  guix 51418c3
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 51418c32d95d8188d8877616829f26479f1135c6
$ $(readlink -f /tmp/guix-science/bin/guix) describe 
guix describe: error: failed to determine origin
hint: Perhaps this `guix' command was not obtained with `guix pull'? Its version string is 51418c32d95d8188d8877616829f26479f1135c6.

$ /tmp/guix-science/bin/guix build python2 <at> 2.4 -n
La jenaj derivoj estus konstruataj:
   /gnu/store/xsk3vg48dfbwcc5w8pn08x5x15n5prpz-python2-2.4.6.drv
   /gnu/store/pnxh0lx28iydhw354xgcfbzk9r6zs6dx-Python-2.4.6.tar.xz.drv
   /gnu/store/fi2my0k9lfag52siz1h7xqwqbzwjkirc-Python-2.4.6.tar.bz2.drv
14.2 MB would be downloaded:
   /gnu/store/6wn346cbw1mh6264v426pwj2klgvxr0z-gcc-5.5.0
$ $(readlink -f /tmp/guix-science/bin/guix) build python2 <at> 2.4 -n
guix build: error: python2: pako ne trovita por versio 2.4
--8<---------------cut here---------------end--------------->8---

Ludo’.

Message #15 received at 45896 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: 45896 <at> debbugs.gnu.org
Cc: Ludovic Courtès <ludo <at> gnu.org>
Subject: [PATCH 1/3] channels: Record 'guix' channel metadata in (guix config).
Date: Wed, 27 Jan 2021 22:51:28 +0100

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.
---
 build-aux/build-self.scm  | 11 ++++--
 guix/channels.scm         | 30 ++++++++++-------
 guix/config.scm.in        | 11 +++++-
 guix/describe.scm         | 28 ++++++++++++++--
 guix/scripts/describe.scm | 70 +++++++++++++++++++--------------------
 guix/self.scm             | 25 +++++++++++---
 6 files changed, 116 insertions(+), 59 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 <at> gnu.org>
+;;; Copyright © 2014, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès <ludo <at> 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"))
diff --git a/guix/channels.scm b/guix/channels.scm
index e7e1eb6fd0..3cc3b4c438 100644
--- a/guix/channels.scm
+++ b/guix/channels.scm
@@ -626,16 +626,23 @@ that unconditionally resumes the continuation."
       (values (run-with-store store mvalue)
               store))))
 
-(define* (build-from-source name source
-                            #:key core verbose? commit
-                            (dependencies '()))
-  "Return a derivation to build Guix from SOURCE, using the self-build script
-contained therein; use COMMIT as the version string.  When CORE is true, build
-package modules under SOURCE using CORE, an instance of Guix."
+(define* (build-from-source instance
+                            #:key core verbose? (dependencies '()))
+  "Return a derivation to build Guix from INSTANCE, using the self-build
+script contained therein.  When CORE is true, build package modules under
+SOURCE using CORE, an instance of Guix."
+  (define name
+    (symbol->string
+     (channel-name (channel-instance-channel instance))))
+  (define source
+    (channel-instance-checkout instance))
+  (define commit
+    (channel-instance-commit instance))
+
   ;; Running the self-build script makes it easier to update the build
   ;; procedure: the self-build script of the Guix-to-be-installed contains the
   ;; right dependencies, build procedure, etc., which the Guix-in-use may not
-  ;; be know.
+  ;; know.
   (define script
     (string-append source "/" %self-build-file))
 
@@ -661,7 +668,9 @@ package modules under SOURCE using CORE, an instance of Guix."
           ;; cause us to redo half of the BUILD computation several times just
           ;; to realize it gives the same result.
           (with-trivial-build-handler
-           (build source #:verbose? verbose? #:version commit
+           (build source
+                  #:verbose? verbose? #:version commit
+                  #:channel-metadata (channel-instance->sexp instance)
                   #:pull-version %pull-version))))
 
       ;; Build a set of modules that extend Guix using the standard method.
@@ -672,10 +681,7 @@ package modules under SOURCE using CORE, an instance of Guix."
   "Return, as a monadic value, the derivation for INSTANCE, a channel
 instance.  DEPENDENCIES is a list of extensions providing Guile modules that
 INSTANCE depends on."
-  (build-from-source (symbol->string
-                      (channel-name (channel-instance-channel instance)))
-                     (channel-instance-checkout instance)
-                     #:commit (channel-instance-commit instance)
+  (build-from-source instance
                      #:core core
                      #:dependencies dependencies))
 
diff --git a/guix/config.scm.in b/guix/config.scm.in
index b2901735d8..223c9eb418 100644
--- a/guix/config.scm.in
+++ b/guix/config.scm.in
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2018, 2019 Ludovic Courtès <ludo <at> gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2018, 2019, 2021 Ludovic Courtès <ludo <at> gnu.org>
 ;;; Copyright © 2017 Caleb Ristvedt <caleb.ristvedt <at> cune.org>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -23,6 +23,8 @@
             %guix-bug-report-address
             %guix-home-page-url
 
+            %channel-metadata
+
             %storedir
             %localstatedir
             %sysconfdir
@@ -56,6 +58,13 @@
 (define %guix-home-page-url
   "@PACKAGE_URL@")
 
+(define %channel-metadata
+  ;; When true, this is an sexp containing metadata for the 'guix' channel
+  ;; this file was built from.  This is used by (guix describe).
+
+  ;; TODO: Implement 'configure.ac' machinery to initialize it.
+  #f)
+
 (define %storedir
   "@storedir@")
 
diff --git a/guix/describe.scm b/guix/describe.scm
index ac89fc0d7c..6a31c707f0 100644
--- a/guix/describe.scm
+++ b/guix/describe.scm
@@ -23,12 +23,13 @@
   #:use-module ((guix utils) #:select (location-file))
   #:use-module ((guix store) #:select (%store-prefix store-path?))
   #:use-module ((guix config) #:select (%state-directory))
-  #:autoload   (guix channels) (sexp->channel)
+  #:autoload   (guix channels) (sexp->channel manifest-entry-channel)
   #:use-module (srfi srfi-1)
   #:use-module (ice-9 match)
   #:export (current-profile
             current-profile-date
             current-profile-entries
+            current-channels
             package-path-entries
 
             package-provenance
@@ -87,10 +88,19 @@ as a number of seconds since the Epoch, or #f if it could not be determined."
                            (string-append (dirname file) "/" target)))))
              (const #f)))))))
 
+(define (channel-metadata)
+  "Return the 'guix' channel metadata sexp from (guix config) if available;
+otherwise return #f."
+  ;; Older 'build-self.scm' would create a (guix config) file without the
+  ;; '%channel-metadata' variable.  Thus, properly deal with a lack of
+  ;; information.
+  (let ((module (resolve-interface '(guix config))))
+    (and=> (module-variable module '%channel-metadata) variable-ref)))
+
 (define current-profile-entries
   (mlambda ()
     "Return the list of entries in the 'guix pull' profile the calling process
-lives in, or #f if this is not applicable."
+lives in, or the empty list if this is not applicable."
     (match (current-profile)
       (#f '())
       (profile
@@ -105,6 +115,20 @@ lives in, or #f if this is not applicable."
               (string=? (manifest-entry-name entry) "guix"))
             (current-profile-entries))))
 
+(define current-channels
+  (mlambda ()
+    "Return the list of channels currently available, including the 'guix'
+channel.  Return the empty list if this information is missing."
+    (match (current-profile-entries)
+      (()
+       ;; As a fallback, if we're not running from a profile, use 'guix'
+       ;; channel metadata from (guix config).
+       (match (channel-metadata)
+         (#f '())
+         (sexp (or (and=> (sexp->channel sexp 'guix) list) '()))))
+      (entries
+       (filter-map manifest-entry-channel entries)))))
+
 (define (package-path-entries)
   "Return two values: the list of package path entries to be added to the
 package search path, and the list to be added to %LOAD-COMPILED-PATH.  These
diff --git a/guix/scripts/describe.scm b/guix/scripts/describe.scm
index e47d207ee0..cd5d3838a8 100644
--- a/guix/scripts/describe.scm
+++ b/guix/scripts/describe.scm
@@ -182,20 +182,18 @@ string is ~a.~%")
                           (current-output-port))))
     (display-package-search-path fmt)))
 
-(define (display-profile-info profile fmt)
+(define* (display-profile-info profile fmt
+                               #:optional
+                               (channels (profile-channels profile)))
   "Display information about PROFILE, a profile as created by (guix channels),
-in the format specified by FMT."
+in the format specified by FMT.  PROFILE can be #f, in which case CHANNELS is
+what matters."
   (define number
-    (generation-number profile))
-
-  (define channels
-    (profile-channels (if (zero? number)
-                          profile
-                          (generation-file-name profile number))))
+    (and profile (generation-number profile)))
 
   (match fmt
     ('human
-     (display-profile-content profile number))
+     (display-profile-content profile number channels))
     ('channels
      (pretty-print `(list ,@(map channel->code channels))))
     ('channels-sans-intro
@@ -213,33 +211,29 @@ in the format specified by FMT."
                   channels))))
   (display-package-search-path fmt))
 
-(define (display-profile-content profile number)
-  "Display the packages in PROFILE, generation NUMBER, in a human-readable
-way and displaying details about the channel's source code."
-  (display-generation profile number)
-  (for-each (lambda (entry)
+(define* (display-profile-content profile number
+                                  #:optional
+                                  (channels (profile-channels profile)))
+  "Display CHANNELS along with PROFILE info, generation NUMBER, in a
+human-readable way and displaying details about the channel's source code.
+PROFILE and NUMBER "
+  (when (and number profile)
+    (display-generation profile number))
+
+  (for-each (lambda (channel)
               (format #t "  ~a ~a~%"
-                      (manifest-entry-name entry)
-                      (manifest-entry-version entry))
-              (match (manifest-entry-channel entry)
-                ((? channel? channel)
-                 (format #t (G_ "    repository URL: ~a~%")
-                         (channel-url channel))
-                 (when (channel-branch channel)
-                   (format #t (G_ "    branch: ~a~%")
-                           (channel-branch channel)))
-                 (format #t (G_ "    commit: ~a~%")
-                         (if (supports-hyperlinks?)
-                             (channel-commit-hyperlink channel)
-                             (channel-commit channel))))
-                (_ #f)))
-
-            ;; Show most recently installed packages last.
-            (reverse
-             (manifest-entries
-              (profile-manifest (if (zero? number)
-                                    profile
-                                    (generation-file-name profile number)))))))
+                      (channel-name channel)
+                      (string-take (channel-commit channel) 7))
+              (format #t (G_ "    repository URL: ~a~%")
+                      (channel-url channel))
+              (when (channel-branch channel)
+                (format #t (G_ "    branch: ~a~%")
+                        (channel-branch channel)))
+              (format #t (G_ "    commit: ~a~%")
+                      (if (supports-hyperlinks?)
+                          (channel-commit-hyperlink channel)
+                          (channel-commit channel))))
+            channels))
 
 (define %vcs-web-views
   ;; Hard-coded list of host names and corresponding web view URL templates.
@@ -295,6 +289,10 @@ text.  The hyperlink links to a web view of COMMIT, when available."
     (with-error-handling
       (match profile
         (#f
-         (display-checkout-info format))
+         (match (current-channels)
+           (()
+            (display-checkout-info format))
+           (channels
+            (display-profile-info #f format channels))))
         (profile
          (display-profile-info (canonicalize-profile profile) format))))))
diff --git a/guix/self.scm b/guix/self.scm
index 15c8ad4eb9..35fba1152d 100644
--- a/guix/self.scm
+++ b/guix/self.scm
@@ -793,7 +793,9 @@ itself."
     (((labels packages _ ...) ...)
      (cons package packages))))
 
-(define* (compiled-guix source #:key (version %guix-version)
+(define* (compiled-guix source #:key
+                        (version %guix-version)
+                        (channel-metadata #f)
                         (pull-version 1)
                         (name (string-append "guix-" version))
                         (guile-version (effective-version))
@@ -977,6 +979,8 @@ itself."
                                          %guix-package-name
                                          #:package-version
                                          version
+                                         #:channel-metadata
+                                         channel-metadata
                                          #:bug-report-address
                                          %guix-bug-report-address
                                          #:home-page-url
@@ -1070,6 +1074,7 @@ itself."
 (define* (make-config.scm #:key gzip xz bzip2
                           (package-name "GNU Guix")
                           (package-version "0")
+                          (channel-metadata #f)
                           (bug-report-address "bug-guix <at> gnu.org")
                           (home-page-url "https://guix.gnu.org"))
 
@@ -1083,6 +1088,7 @@ itself."
                                %guix-version
                                %guix-bug-report-address
                                %guix-home-page-url
+                               %channel-metadata
                                %system
                                %store-directory
                                %state-directory
@@ -1125,6 +1131,11 @@ itself."
                    (define %guix-bug-report-address #$bug-report-address)
                    (define %guix-home-page-url #$home-page-url)
 
+                   (define %channel-metadata
+                     ;; Metadata for the 'guix' channel in use.  This
+                     ;; information is used by (guix describe).
+                     '#$channel-metadata)
+
                    (define %gzip
                      #+(and gzip (file-append gzip "/bin/gzip")))
                    (define %bzip2
@@ -1249,11 +1260,14 @@ containing MODULE-FILES and possibly other files as well."
 
 (define* (guix-derivation source version
                           #:optional (guile-version (effective-version))
-                          #:key (pull-version 0))
+                          #:key (pull-version 0)
+                          channel-metadata)
   "Return, as a monadic value, the derivation to build the Guix from SOURCE
-for GUILE-VERSION.  Use VERSION as the version string.  PULL-VERSION specifies
-the version of the 'guix pull' protocol.  Return #f if this PULL-VERSION value
-is not supported."
+for GUILE-VERSION.  Use VERSION as the version string.  Use CHANNEL-METADATA
+as the channel metadata sexp to include in (guix config).
+
+PULL-VERSION specifies the version of the 'guix pull' protocol.  Return #f if
+this PULL-VERSION value is not supported."
   (define (shorten version)
     (if (and (string-every char-set:hex-digit version)
              (> (string-length version) 9))
@@ -1278,6 +1292,7 @@ is not supported."
     (set-guile-for-build guile)
     (let ((guix (compiled-guix source
                                #:version version
+                               #:channel-metadata channel-metadata
                                #:name (string-append "guix-"
                                                      (shorten version))
                                #:pull-version pull-version
-- 
2.30.0

Message #18 received at 45896 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: 45896 <at> debbugs.gnu.org
Cc: Ludovic Courtès <ludo <at> gnu.org>
Subject: [PATCH 3/3] gnu: guix: Pass the '--with-channel-commit' configure
 flag.
Date: Wed, 27 Jan 2021 22:51:30 +0100

* gnu/packages/package-management.scm (guix)[arguments]: Add
'--with-channel-commit' to #:configure-flags.
---
 gnu/packages/package-management.scm | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/gnu/packages/package-management.scm b/gnu/packages/package-management.scm
index 60d8d4b8c6..dfb4b868ee 100644
--- a/gnu/packages/package-management.scm
+++ b/gnu/packages/package-management.scm
@@ -154,6 +154,13 @@
       (build-system gnu-build-system)
       (arguments
        `(#:configure-flags (list
+
+                            ;; Provide channel metadata for 'guix describe'.
+                            ;; Don't pass '--with-channel-url' and
+                            ;; '--with-channel-introduction' and instead use
+                            ;; the defaults.
+                            ,(string-append "--with-channel-commit=" commit)
+
                             "--localstatedir=/var"
                             "--sysconfdir=/etc"
                             (string-append "--with-bash-completion-dir="
-- 
2.30.0

Message #21 received at 45896 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: 45896 <at> debbugs.gnu.org
Cc: Ludovic Courtès <ludo <at> gnu.org>
Subject: [PATCH 2/3] build: Add '--with-channel-commit' and related configure
 flags.
Date: Wed, 27 Jan 2021 22:51:29 +0100

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

* m4/guix.m4 (GUIX_CHANNEL_METADATA): New macro.
* configure.ac: Use it.
* guix/config.scm.in (%channel-metadata): Adjust accordingly.
---
 configure.ac       |  1 +
 guix/config.scm.in | 20 +++++++++++++++++---
 m4/guix.m4         | 30 +++++++++++++++++++++++++++++-
 3 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/configure.ac b/configure.ac
index aa97f67ebe..aa60471143 100644
--- a/configure.ac
+++ b/configure.ac
@@ -25,6 +25,7 @@ AM_GNU_GETTEXT_VERSION([0.18.1])
 
 GUIX_SYSTEM_TYPE
 GUIX_ASSERT_SUPPORTED_SYSTEM
+GUIX_CHANNEL_METADATA
 
 AM_CONDITIONAL([CROSS_COMPILING], [test "x$cross_compiling" = "xyes"])
 
diff --git a/guix/config.scm.in b/guix/config.scm.in
index 223c9eb418..d582d91d74 100644
--- a/guix/config.scm.in
+++ b/guix/config.scm.in
@@ -61,9 +61,23 @@
 (define %channel-metadata
   ;; When true, this is an sexp containing metadata for the 'guix' channel
   ;; this file was built from.  This is used by (guix describe).
-
-  ;; TODO: Implement 'configure.ac' machinery to initialize it.
-  #f)
+  (let ((url    @GUIX_CHANNEL_URL@)
+        (commit @GUIX_CHANNEL_COMMIT@)
+        (intro  @GUIX_CHANNEL_INTRODUCTION@))
+    (and url commit
+         `(repository
+           (version 0)
+           (url ,url)
+           (branch "master")                      ;XXX: doesn't really matter
+           (commit ,commit)
+           (name guix)
+           ,@(if intro
+                 `((introduction
+                    (channel-introduction
+                     (version 0)
+                     (commit ,(car intro))
+                     (signer ,(cdr intro)))))
+                 '())))))
 
 (define %storedir
   "@storedir@")
diff --git a/m4/guix.m4 b/m4/guix.m4
index f8eb5aaf51..c1ce0876fa 100644
--- a/m4/guix.m4
+++ b/m4/guix.m4
@@ -1,5 +1,5 @@
 dnl GNU Guix --- Functional package management for GNU
-dnl Copyright © 2012, 2013, 2014, 2015, 2016, 2018, 2019, 2020 Ludovic Courtès <ludo <at> gnu.org>
+dnl Copyright © 2012, 2013, 2014, 2015, 2016, 2018, 2019, 2020, 2021 Ludovic Courtès <ludo <at> gnu.org>
 dnl Copyright © 2014 Mark H Weaver <mhw <at> netris.org>
 dnl Copyright © 2017 Efraim Flashner <efraim <at> flashner.co.il>
 dnl
@@ -398,3 +398,31 @@ that of the existing installation '$guix_cv_current_localstatedir'])
       esac
     fi
   fi])
+
+dnl GUIX_CHANNEL_METADATA
+dnl
+dnl Provide the channel metadata for this build.  This allows 'guix describe'
+dnl to return meaningful data, as it would for a 'guix pull'-provided 'guix'.
+dnl The default URL and introduction are taken from (guix channels).
+AC_DEFUN([GUIX_CHANNEL_METADATA], [
+  AC_ARG_WITH([channel-url], [AS_HELP_STRING([--with-channel-url=URL],
+    [assert that this is built from the Git repository at URL])],
+    [guix_channel_url="\"$withval\""],
+    [guix_channel_url="\"https://git.savannah.gnu.org/git/guix.git\""])
+  AC_ARG_WITH([channel-commit], [AS_HELP_STRING([--with-channel-commit=COMMIT],
+    [assert that this is built from COMMIT])],
+    [guix_channel_commit="\"$withval\""],
+    [guix_channel_commit="#f"])
+  AC_ARG_WITH([channel-introduction], [AS_HELP_STRING([--with-channel-introduction=COMMIT:FINGERPRINT],
+    [specify COMMIT and FINGERPRINT as the introduction of this channel])],
+    [guix_channel_introduction="'(\"`echo $withval | cut -f1 -d:`\" \"`echo $withval | cut -f2 -d:`\")"],
+    [guix_channel_introduction="'(\"9edb3f66fd807b096b48283debdcddccfea34bad\" . \"BBB0 2DDF 2CEA F6A8 0D1D  E643 A2A0 6DF2 A33A 54FA\")"])
+
+  GUIX_CHANNEL_URL="$guix_channel_url"
+  GUIX_CHANNEL_COMMIT="$guix_channel_commit"
+  GUIX_CHANNEL_INTRODUCTION="$guix_channel_introduction"
+
+  AC_SUBST([GUIX_CHANNEL_URL])
+  AC_SUBST([GUIX_CHANNEL_COMMIT])
+  AC_SUBST([GUIX_CHANNEL_INTRODUCTION])
+])
-- 
2.30.0

Message #24 received at 45896 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: 45896 <at> debbugs.gnu.org
Subject: Re: bug#45896: Non-pull ‘guix’ should know
 its channels
Date: Wed, 27 Jan 2021 22:53:05 +0100

Ludovic Courtès <ludo <at> gnu.org> skribis:

> This problem extends beyond that: channel modules are not found if the
> symlink is dereferenced:

In fact, this is “by design”, so nothing particularly worrying, after all.

Ludo’.

Message #27 received at 45896 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: 45896 <at> debbugs.gnu.org
Subject: Re: bug#45896: Non-pull ‘guix’ should know
 its channels
Date: Wed, 27 Jan 2021 22:53:47 +0100

These patches depend on <https://issues.guix.gnu.org/45919>.

Message #36 received at 45896-done <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: 45896-done <at> debbugs.gnu.org
Subject: Re: bug#45896: Non-pull ‘guix’ should know
 its channels
Date: Thu, 04 Feb 2021 13:46:33 +0100

Patches pushed as 8ecc265c5c6519986758567682726647850d5d03.

Ludo’.

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