kernel: Obtain and display channel info from the inferior.

* guix-jupyter-kernel.scm (reply-for-channels): Add #:profile parameter
and honor it.
(reply-execute-request): Call 'inferior-eval' and pass #:profile to
'reply-for-channels'.

guix-jupyter-kernel.scm

@@ -174,12 +174,17 @@ NAME with MANIFEST."
                channels)))))
 
 (define* (reply-for-channels kernel message channels
-                             #:key (count 0))
-  "Reply to MESSAGE, which comes from KERNEL, that we successfully switch to
-CHANNELS."
-  (reply-html kernel message
-              (sxml->html-string (channels->shtml channels))
-              count))
+                             #:key profile (count 0))
+  "Reply to MESSAGE, which comes from KERNEL, that we successfully switched
+to CHANNELS in PROFILE."
+  (let ((instances (if profile
+                       (match (profile-channels profile)
+                         (()  channels)
+                         (lst lst))
+                       channels)))
+    (reply-html kernel message
+                (sxml->html-string (channels->shtml instances))
+                count)))
 
 (define* (reply-for-channel-failure kernel message channels error
                                     #:key (count 0))
@@ -409,10 +414,13 @@ stripped."
          ;; TODO: Send a message showing that something's happening.
          (catch 'git-error
            (lambda ()
-             (let ((inferior (inferior-for-channels channels)))
-               ;; TODO: Obtain the <channel-instance> records so the message
-               ;; can provide more info.
+             (let* ((inferior (inferior-for-channels channels))
+                    (profile  (inferior-eval '(begin
+                                                (use-modules (guix describe))
+                                                (current-profile))
+                                             inferior)))
                (reply-for-channels kernel message channels
+                                   #:profile profile
                                    #:count count)
                (set-proxy-state-inferior (increment-execution-count state)
                                          inferior)))