publish: Add advertising support.

* guix/scripts/publish.scm (%options): Add "--advertise" option.
(show-help): Document it.
(service-name): New procedure,
(publish-service-type): new variable.
(run-publish-server): Add "advertise?" and "port" parameters. Use them to publish
the server using Avahi.
(guix-publish): Pass the "advertise?" option to "run-publish-server".
* gnu/services/base.scm (<guix-publish-configuration>): Add "advertise?"
field.
(guix-publish-shepherd-service): Honor it.

1 files changed, 5 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index baf6e69039a..8ca243004a5 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -12159,6 +12159,11 @@ The signing key pair must be generated before @command{guix publish} is
 launched, using @command{guix archive --generate-key} (@pxref{Invoking
 guix archive}).
 
+When the @option{--advertise} option is passed, the server advertises
+its availability on the local network using multicast DNS (mDNS) and DNS
+service discovery (DNS-SD), currently @i{via} Guile-Avahi (@pxref{Top,,,
+guile-avahi, Using Avahi in Guile Scheme Programs}).
+
 The general syntax is:
 
 @example