guix package: Add '--export-channels'.

* guix/channels.scm (sexp->channel): Export.
* guix/describe.scm: Use (guix channels).
(manifest-entry-provenance): New procedure.
* guix/scripts/package.scm (channel=?, export-channels): New
procedures.
(show-help, %options): Add '--export-channels'.
(process-query): Honor it.
* build-aux/build-self.scm (build-program)[select?]: Exclude (guix
channels) to account for the (guix describe) change above.
* doc/guix.texi (Invoking guix package): Document it.

1 files changed, 61 insertions, 0 deletions

diff --git a/guix/scripts/package.scm b/guix/scripts/package.scm
index 2b52016c67..8234a1703d 100644
--- a/guix/scripts/package.scm
+++ b/guix/scripts/package.scm
@@ -43,6 +43,7 @@
   #:use-module (guix scripts build)
   #:use-module (guix transformations)
   #:use-module (guix describe)
+  #:autoload   (guix channels) (channel-name channel-commit channel->code)
   #:autoload   (guix store roots) (gc-roots user-owned?)
   #:use-module ((guix build utils)
                 #:select (directory-exists? mkdir-p))
@@ -363,6 +364,54 @@ Alternately, see @command{guix package --search-paths -p ~s}.")
                  (pretty-print exp port))
                exp))))
 
+(define (channel=? a b)
+  (and (channel-commit a) (channel-commit b)
+       (string=? (channel-commit a) (channel-commit b))))
+
+(define* (export-channels manifest
+                          #:optional (port (current-output-port)))
+  (define channels
+    (delete-duplicates
+     (append-map manifest-entry-provenance (manifest-entries manifest))
+     channel=?))
+
+  (define channel-names
+    (delete-duplicates (map channel-name channels)))
+
+  (define table
+    (fold (lambda (channel table)
+            (vhash-consq (channel-name channel) channel table))
+          vlist-null
+          channels))
+
+  (when (null? channels)
+    (leave (G_ "no provenance information for this profile~%")))
+
+  (format port (G_ "\
+;; This channel file can be passed to 'guix pull -C' or to
+;; 'guix time-machine -C' to obtain the Guix revision that was
+;; used to populate this profile.\n"))
+  (newline port)
+  (display "(list\n" port)
+  (for-each (lambda (name)
+              (define indent "     ")
+              (match (vhash-foldq* cons '() name table)
+                ((channel extra ...)
+                 (unless (null? extra)
+                   (display indent port)
+                   (format port (G_ "\
+;; Note: these other commits were also used to install \
+some of the packages in this profile:~%"))
+                   (for-each (lambda (channel)
+                               (format port "~a;;   ~s~%"
+                                       indent (channel-commit channel)))
+                             extra))
+                 (pretty-print (channel->code channel) port
+                               #:per-line-prefix indent))))
+            channel-names)
+  (display ")\n" port)
+  #t)
+
 
 ;;;
 ;;; Command-line options.
@@ -419,6 +468,8 @@ Install, remove, or upgrade packages in a single transaction.\n"))
   (display (G_ "
       --export-manifest  print a manifest for the chosen profile"))
   (display (G_ "
+      --export-channels  print channels for the chosen profile"))
+  (display (G_ "
   -p, --profile=PROFILE  use PROFILE instead of the user's default profile"))
   (display (G_ "
       --list-profiles    list the user's profiles"))
@@ -556,6 +607,10 @@ kind of search path~%")
                  (lambda (opt name arg result arg-handler)
                    (values (cons `(query export-manifest) result)
                            #f)))
+         (option '("export-channels") #f #f
+                 (lambda (opt name arg result arg-handler)
+                   (values (cons `(query export-channels) result)
+                           #f)))
          (option '(#\p "profile") #t #f
                  (lambda (opt name arg result arg-handler)
                    (values (alist-cons 'profile (canonicalize-profile arg)
@@ -882,6 +937,12 @@ processed, #f otherwise."
          (export-manifest manifest (current-output-port))
          #t))
 
+      (('export-channels)
+       (let ((manifest (concatenate-manifests
+                        (map profile-manifest profiles))))
+         (export-channels manifest (current-output-port))
+         #t))
+
       (_ #f))))