services: guix: Add 'set-http-proxy' action.

Fixes <https://bugs.gnu.org/25569>.
Reported by Divan Santana <divan@santanas.co.za>.

* gnu/services/base.scm (shepherd-set-http-proxy-action): New procedure.
(guix-shepherd-service): Add 'actions' field.  Change 'start' to a
lambda; check the value of the "http_proxy" environment variable and
add "http_proxy" and "https_proxy" to #:environment-variables as a
function of that.
* gnu/tests/base.scm (run-basic-test)["guix-daemon set-http-proxy
action", "guix-daemon set-http-proxy action, clear"]: New tests.
* doc/guix.texi (Base Services): Document it.

1 files changed, 17 insertions, 2 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 450ca3c5d8..7169e03516 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -12779,9 +12779,24 @@ List of extra command-line options for @command{guix-daemon}.
 File where @command{guix-daemon}'s standard output and standard error
 are written.
 
+@cindex HTTP proxy, for @code{guix-daemon}
+@cindex proxy, for @code{guix-daemon} HTTP access
 @item @code{http-proxy} (default: @code{#f})
-The HTTP proxy used for downloading fixed-output derivations and
-substitutes.
+The URL of the HTTP and HTTPS proxy used for downloading fixed-output
+derivations and substitutes.
+
+It is also possible to change the daemon's proxy at run time through the
+@code{set-http-proxy} action, which restarts it:
+
+@example
+herd set-http-proxy guix-daemon http://localhost:8118
+@end example
+
+To clear the proxy settings, run:
+
+@example
+herd set-http-proxy guix-daemon
+@end example
 
 @item @code{tmpdir} (default: @code{#f})
 A directory path where the @command{guix-daemon} will perform builds.