build: Add `sync-synopses.scm'.

* build-aux/sync-synopses.scm: New file.
* Makefile.am (EXTRA_DIST): Add it.
  (dist-hook): New target.

Makefile.am

@@ -319,6 +319,7 @@ EXTRA_DIST =					\
   .dir-locals.el				\
   hydra.scm					\
   build-aux/download.scm			\
+  build-aux/sync-synopses.scm			\
   srfi/srfi-64.scm				\
   srfi/srfi-64.upstream.scm			\
   tests/test.drv				\
@@ -366,3 +367,7 @@ AM_DISTCHECK_CONFIGURE_FLAGS =			\
   --with-libgcrypt-prefix="$(LIBGCRYPT_PREFIX)"	\
   --with-nix-prefix="$(NIX_PREFIX)"		\
   --enable-daemon
+
+dist-hook:
+	-$(top_builddir)/pre-inst-env $(GUILE)		\
+	   $(top_srcdir)/build-aux/sync-synopses.scm

build-aux/sync-synopses.scm

@@ -0,0 +1,61 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2013 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/>.
+
+;;;
+;;; Report synopses that defer from those found in the GNU Womb.
+;;;
+
+(use-modules (guix gnu-maintenance)
+             (guix packages)
+             (guix utils)
+             (guix ui)
+             (gnu packages)
+             (srfi srfi-1)
+             (srfi srfi-26)
+             (ice-9 match))
+
+(define official
+  ;; GNU package descriptors from the Womb.
+  (official-gnu-packages))
+
+(define gnus
+  ;; GNU packages available in the distro.
+  (let ((lookup (lambda (p)
+                  (find (lambda (descriptor)
+                          (equal? (gnu-package-name descriptor)
+                                  (package-name p)))
+                        official))))
+    (fold-packages (lambda (package result)
+                     (or (and=> (lookup package)
+                                (cut alist-cons package <> result))
+                         result))
+                   '())))
+
+;; Iterate over GNU packages.  Report those whose synopsis defers from that
+;; found upstream.
+(for-each (match-lambda
+           ((package . descriptor)
+            (let ((upstream   (gnu-package-doc-summary descriptor))
+                  (downstream (package-synopsis package))
+                  (loc        (package-location package)))
+              (unless (and upstream (string=? upstream downstream))
+                (format (guix-warning-port)
+                        "~a: ~a: proposed synopsis: ~s~%"
+                        (location->string loc) (package-name package)
+                        upstream)))))
+          gnus)