Complete package names.

* guix-jupyter-kernel.scm (reply-complete-request): Handle package name
completion after "guix environment _ <-".

guix-jupyter-kernel.scm

@@ -34,6 +34,7 @@
              (guix gexp)
              (guix store)
              (guix derivations)
+             (guix inferior)
              (guix monads)
              (guix modules)
              (guix profiles)
@@ -339,6 +340,13 @@ Return STATE."
                                              names)
                                      (- cursor (string-length prefix))
                                      cursor))))
+          ((";;guix" "environment" _ "<-" _ ... prefix)
+           (match (inferior-available-packages (force %inferior))
+             (((names . _) ...)
+              (send-completion-reply (filter (cut string-prefix? prefix <>)
+                                             names)
+                                     (- cursor (string-length prefix))
+                                     cursor))))
           (_
            (format/log "ignoring completion request~%")
            #f))