Make the `C-c C-n' command in Message more sturdy

[gnus] / lisp / message.el

diff --git a/lisp/message.el b/lisp/message.el
index 1fea5f9..12002b6 100644 (file)
--- a/lisp/message.el
+++ b/lisp/message.el
@@ -3336,11 +3336,33 @@ or in the synonym headers, defined by `message-header-synonyms'."
 (defun message-insert-newsgroups ()
   "Insert the Newsgroups header from the article being replied to."
   (interactive)
-  (when (and (message-position-on-field "Newsgroups")
-            (mail-fetch-field "newsgroups")
-            (not (string-match "\\` *\\'" (mail-fetch-field "newsgroups"))))
-    (insert ","))
-  (insert (or (message-fetch-reply-field "newsgroups") "")))
+  (let ((old-newsgroups (mail-fetch-field "newsgroups"))
+       (new-newsgroups (message-fetch-reply-field "newsgroups"))
+       (first t)
+       insert-newsgroups)
+    (message-position-on-field "Newsgroups")
+    (cond
+     ((not new-newsgroups)
+      (error "No Newsgroups to insert"))
+     ((not old-newsgroups)
+      (insert new-newsgroups))
+     (t
+      (setq new-newsgroups (split-string new-newsgroups "[, ]+")
+           old-newsgroups (split-string old-newsgroups "[, ]+"))
+      (dolist (group new-newsgroups)
+       (unless (member group old-newsgroups)
+         (push group insert-newsgroups)))
+      (if (null insert-newsgroups)
+         (error "Newgroup%s already in the header"
+                (if (> (length new-newsgroups) 1)
+                    "s" ""))
+       (when old-newsgroups
+         (setq first nil))
+       (dolist (group insert-newsgroups)
+         (unless first
+           (insert ","))
+         (setq first nil)
+         (insert group)))))))
 
 \f