Add jupyter-comm-id

Used to get an identification string of the connection that a kernel client is
using.

jupyter-comm-layer.el

@@ -100,6 +100,12 @@ called if needed. This means that a call to
 By default, on the last OBJ removed, `jupyter-comm-stop' is
 called if needed.")
 
+(cl-defgeneric jupyter-comm-id ((comm jupyter-comm-layer))
+  "Return an identification string for COMM.
+Can be used to identify this communication channel. For example,
+used in `jupyter-repl-scratch-buffer' to name the scratch
+buffer.")
+
 (cl-defgeneric jupyter-event-handler (_obj _event)
   "Handle EVENT using OBJ."
   nil)
@@ -218,6 +224,11 @@ called if needed.")
     (error "Need threading support"))
   (cl-call-next-method))
 
+(cl-defmethod jupyter-comm-id ((comm jupyter-sync-channel-comm))
+  (format "session=%s" (truncate-string-to-width
+                        (jupyter-session-id (oref comm session))
+                        9 nil nil "…")))
+
 (defun jupyter-sync-channel-comm--check (comm)
   (condition-case err
       (cl-loop
@@ -357,6 +368,11 @@ called if needed.")
   (cl-call-next-method)
   (oset comm ioloop (jupyter-channel-ioloop)))
 
+(cl-defmethod jupyter-comm-id ((comm jupyter-channel-ioloop-comm))
+  (format "session=%s" (truncate-string-to-width
+                        (jupyter-session-id (oref comm session))
+                        9 nil nil "…")))
+
 (cl-defmethod jupyter-initialize-connection ((comm jupyter-channel-ioloop-comm)
                                              (session jupyter-session))
   (cl-call-next-method)

jupyter-repl.el

@@ -1638,10 +1638,8 @@ Return the buffer switched to."
   (interactive)
   (if (jupyter-repl-connected-p)
       (let* ((client jupyter-current-client)
-             (name (format "*jupyter-scratch[session=%s]*"
-                           (truncate-string-to-width
-                            (jupyter-session-id (oref client session))
-                            9 nil nil "…"))))
+             (name (format "*jupyter-scratch[%s]*"
+                           (jupyter-comm-id (oref client kcomm)))))
         (unless (get-buffer name)
           (with-current-buffer (get-buffer-create name)
             (funcall (jupyter-kernel-language-mode client))