etc: Add 'disarchive-manifest.scm'.

* etc/disarchive-manifest.scm: New file.
* Makefile.am (EXTRA_DIST): Add it.

Makefile.am

@@ -624,6 +624,7 @@ EXTRA_DIST +=						\
   .guix-authorizations					\
   .guix-channel						\
   scripts/guix.in					\
+  etc/disarchive-manifest.scm				\
   etc/guix-install.sh					\
   etc/news.scm						\
   etc/release-manifest.scm				\

etc/disarchive-manifest.scm

@@ -0,0 +1,112 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 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/>.
+
+;;; This file returns a manifest that builds a directory containing Disarchive
+;;; metadata for all the tarballs packages refer to.
+
+(use-modules (srfi srfi-1) (ice-9 match)
+             (guix packages) (guix gexp) (guix profiles)
+             (guix base16)
+             (gnu packages))
+
+(include "source-manifest.scm")
+
+(define (tarball-origin? origin)
+  (match (origin-actual-file-name origin)
+    (#f #f)
+    ((? string? file)
+     ;; As of version 0.2.1, Disarchive can only deal with raw tarballs and
+     ;; gzip-compressed tarballs.
+     (and (origin-hash origin)
+          (or (string-suffix? ".tar.gz" file)
+              (string-suffix? ".tgz" file)
+              (string-suffix? ".tar" file))))))
+
+(define (origin->disarchive origin)
+  "Return a directory containing Disarchive metadata for ORIGIN, a tarball, or
+an empty directory if ORIGIN could not be disassembled."
+  (define file-name
+    (let ((hash (origin-hash origin)))
+      (string-append (symbol->string (content-hash-algorithm hash))
+                     "/"
+                     (bytevector->base16-string
+                      (content-hash-value hash)))))
+
+  (define disarchive
+    (specification->package "disarchive"))
+
+  (define build
+    (with-imported-modules '((guix build utils))
+      #~(begin
+          (use-modules (guix build utils)
+                       (srfi srfi-34))
+
+          (define tarball
+            #+(upstream-origin origin))
+
+          (define file-name
+            (string-append #$output "/" #$file-name))
+
+          (define profile
+            #+(profile (content (packages->manifest (list disarchive)))))
+
+          (mkdir-p (dirname file-name))
+          (setenv "PATH" (string-append profile "/bin"))
+          (setenv "GUILE_LOAD_PATH"
+                  (string-append profile "/share/guile/site/"
+                                 (effective-version)))
+          (setenv "GUILE_LOAD_COMPILED_PATH"
+                  (string-append profile "/lib/guile/" (effective-version)
+                                 "/site-ccache"))
+
+          (guard (c ((invoke-error? c)
+                     ;; Sometimes Disarchive fails with "could not find Gzip
+                     ;; compressor".  When that happens, produce an empty
+                     ;; directory instead of failing.
+                     (report-invoke-error c)
+                     (delete-file file-name)))
+            (with-output-to-file file-name
+              (lambda ()
+                ;; Disarchive records the tarball name in its output.  Thus,
+                ;; strip the hash from TARBALL.
+                (let ((short-name (strip-store-file-name tarball)))
+                  (symlink tarball short-name)
+                  (invoke "disarchive" "disassemble" short-name))))))))
+
+  (computed-file (match (origin-actual-file-name origin)
+                   ((? string? str) (string-append str ".dis"))
+                   (#f "anonymous-tarball.dis"))
+                 build))
+
+(define (disarchive-collection origins)
+  "Return a directory containing all the Disarchive metadata for ORIGINS."
+  (directory-union "disarchive-collection"
+                   (filter-map (lambda (origin)
+                                 (and (tarball-origin? origin)
+                                      (origin->disarchive origin)))
+                               origins)
+                   #:copy? #t))
+
+
+;; The manifest containing Disarchive data.
+(let ((origins (all-origins)))
+  (manifest
+   (list (manifest-entry
+           (name "disarchive-collection")
+           (version (length origins))
+           (item (disarchive-collection origins))))))