pull: Distinguish "already up to date" from "updated".

* guix/ui.scm (show-what-to-build): Return (length req*).
* guix/scripts/pull.scm (guix-pull): Print an "already up to date"
  message when there's nothing to build.

1 files changed, 12 insertions, 8 deletions

diff --git a/guix/scripts/pull.scm b/guix/scripts/pull.scm
index 42ff525524..942bf501c5 100644
--- a/guix/scripts/pull.scm
+++ b/guix/scripts/pull.scm
@@ -216,12 +216,16 @@ Download and deploy the latest version of Guix.\n"))
                         ((source-dir)
                          (derivation-output-path
                           (assoc-ref (derivation-outputs drv) "out"))))
-            (show-what-to-build store (list source))
-            (if (build-derivations store (list source))
-                (let ((latest (string-append config-dir "/latest")))
-                  (add-indirect-root store latest)
-                  (switch-symlinks latest source-dir)
-                  (format #t
-                          (_ "updated ~a successfully deployed under `~a'~%")
-                          %guix-package-name latest)
+            (if (show-what-to-build store (list source))
+                (if (build-derivations store (list source))
+                    (let ((latest (string-append config-dir "/latest")))
+                      (add-indirect-root store latest)
+                      (switch-symlinks latest source-dir)
+                      (format #t
+                              (_ "updated ~a successfully deployed under `~a'~%")
+                              %guix-package-name latest)
+                      #t)
+                    (leave (_ "failed to update Guix, check the build log~%")))
+                (begin
+                  (display (_ "Guix already up to date\n"))
                   #t))))))))