guix-install.sh: Prompt for configuring substitutes discovery.

Also ensure prompt_yes_no always print the message with a trailing space,
which is more pleasing to the eye.

* etc/guix-daemon.conf.in <--discover=no>: New guix-daemon option.
* etc/guix-daemon.service.in: Likewise.
* etc/init.d/guix-daemon.in: Likewise.
* etc/openrc/guix-daemon.in: Likewise.
* etc/guix-install.sh (configure_substitute_discovery): New procedure.
(sys_enable_guix_daemon): Ask the user whether automatic substitute discovery
should be enabled.  Set the '--discover' argument accordingly.
(prompt_yes_no): Add a trailing space to the message.
(sys_authorize_build_farms): Remove trailing space from the message argument.
* NEWS (Distribution): Add news.

1 files changed, 2 insertions, 1 deletions

diff --git a/etc/guix-daemon.service.in b/etc/guix-daemon.service.in
index 407cdd199c8..17b54eaeb06 100644
--- a/etc/guix-daemon.service.in
+++ b/etc/guix-daemon.service.in
@@ -6,7 +6,8 @@
 Description=Build daemon for GNU Guix
 
 [Service]
-ExecStart=@localstatedir@/guix/profiles/per-user/root/current-guix/bin/guix-daemon --build-users-group=guixbuild
+ExecStart=@localstatedir@/guix/profiles/per-user/root/current-guix/bin/guix-daemon \
+    --build-users-group=guixbuild --discover=no
 Environment='GUIX_LOCPATH=@localstatedir@/guix/profiles/per-user/root/guix-profile/lib/locale' LC_ALL=en_US.utf8
 RemainAfterExit=yes
 StandardOutput=syslog