doc: Add detailed usage instructions for the announce-gen script.

And update the about.txt boilerplate text.

* doc/release.org (Update the on-line copy of the manual): Add a note
about restarting mcron after reconfiguring.
(Prepare the email announcement): Add usage instructions for
announce-gen.  Reword to explicit that appending NEWS should have been
handled by the announce-gen script.

doc/announcements/savannah/about.txt

@@ -1,7 +1,17 @@
-== About GNU Guix ==
+• About
 
-[http://www.gnu.org/software/guix GNU Guix] is a transactional package manager for the GNU system.  The Guix System Distribution or GuixSD is an advanced distribution of the GNU system that relies on GNU Guix and [http://www.gnu.org/distros/free-system-distribution-guidelines.html respects the user's freedom].
+GNU Guix is a transactional package manager and an advanced
+distribution of the GNU system that respects user freedom.  Guix can
+be used on top of any system running the Hurd or the Linux kernel, or
+it can be used as a standalone operating system distribution for i686,
+x86_64, ARMv7, AArch64 and POWER9 machines.
 
-In addition to standard package management features, Guix supports transactional upgrades and roll-backs, unprivileged package management, per-user profiles, and garbage collection.  Guix uses low-level mechanisms from the Nix package manager, except that packages are defined as native [http://www.gnu.org/software/guile Guile] modules, using extensions to the [http://schemers.org Scheme] language.  GuixSD offers a declarative approach to operating system configuration management, and is highly customizable and hackable.
+In addition to standard package management features, Guix supports
+transactional upgrades and roll-backs, unprivileged package
+management, per-user profiles, and garbage collection.  When used as a
+standalone GNU/Linux distribution, Guix offers a declarative,
+stateless approach to operating system configuration management.  Guix
+is highly customizable and hackable through Guile programming
+interfaces and extensions to the Scheme language.
 
-GuixSD can be used on an i686 or x86_64 machine.  It is also possible to use Guix on top of an already installed GNU/Linux system, including on mips64el and armv7.
+https://guix.gnu.org

doc/release.org

@@ -1,5 +1,5 @@
 #+TITLE: Release Process for GNU Guix
-#+AUTHOR: Ludovic Courtès
+#+AUTHOR: Ludovic Courtès, Maxim Cournoyer
 #+STARTUP: content hidestars
 #+EMAIL: ludo@gnu.org
 
@@ -197,14 +197,33 @@ The web site will be automatically rebuilt by an mcron job on berlin
 ** Update the on-line copy of the manual
 
 Change the ‘static-web-site’ service in hydra/berlin.scm
-(guix-maintenance.git) so that it builds the ‘version-X.Y.Z’ branch.
+(guix-maintenance.git) and reconfigure berlin, so that it builds the
+‘version-X.Y.Z’ branch.
+
+Note: Simply reconfiguring is *not* enough to ensure the new manual
+will be built.  You must also restart the mcron service for the update
+job to take effect.
 
 ** Prepare the email announcement
 
-  $ build-aux/announce-gen --release-type=alpha --package-name=guix \
-      --previous-version=X1.Y1.Z1 --current-version=X2.Y2.Z2 \
+The following command uses the =build-aux/announce-gen= script found
+in the ~gnulib~ sources.  By default, it will match only release
+artifacts named '${package-name}-${version}',
+e.g. 'guix-1.3.0.tar.gz'.  Since Guix includes various other artifacts
+such as ISO and QCOW2 images, it is useful to modify the script with
+the following command:
+
+  $ sed -E 's/(my @tarballs = ).*/\1glob("*.[xlg]z *.qcow2 *.iso");/' \
+      -i ~/.local/bin/announce-gen
+
+The script must run from the release sub-directory containing the
+release artifacts, like so:
+
+  $ cd release-X.Y.Z
+  $ announce-gen --release-type=stable --package-name=guix \
+      --previous-version=X1.Y1.Z1 --current-version=X.Y.Z \
       --gpg-key-id=MY-KEY --url-directory=https://ftp.gnu.org/gnu/guix \
-      --bootstrap-tools=autoconf,automake,makeinfo,help2man
+      --news=../NEWS
 
 The subject must be "GNU Guix X.Y.Z released".  The text should remain
 formal and impersonal (it is sent on behalf of the Guix and GNU
@@ -212,9 +231,9 @@ projects.)  It must include a description of what Guix is (not everyone
 reading info-gnu may know about it.)  Use the text of previous
 announcements as a template.
 
-Below the initial boilerplate that describes Guile should come the
-output of `announce-gen', and then the `NEWS' file excerpt in its
-entirety (don't call it a change log since that's not what it is.)
+Below the initial [[file:announcements/savannah/about.txt]["About" section boilerplate]] that describes Guix
+should come the output of ~announce-gen~, which should include the
+NEWS content for the release.
 
 ** Send the email announcement