message: Clean up bogus GitHub recipients

.emacs.d/lisp/init-message.el

@@ -66,15 +66,44 @@ systematically send encrypted emails when possible."
 (add-hook 'message-send-hook #'ambrevar/message-sign-encrypt-if-all-keys-trusted)
 
 
-;; Fix replying to GitHub.  TODO: Does not work.
-(defun ambrevar/message-alter-bogus-github-recipients (addrcell)
-  "Discard @reply.github.com mail addresses.
-ADDRCELL is a cons cell where the car is the mail address and the
-cdr is the complete address (full name and mail address)."
-  (unless (string-match (rx "@noreply.github.com" string-end)
-                        (cdr addrcell))
-    addrcell))
-(setq message-alter-recipients-function 'ambrevar/message-alter-bogus-github-recipients)
+;; Fix replying to GitHub.
+;; We could leverage `message-alter-recipients-function' but it does not seem to
+;; be called with Notmuch for instance.
+(defun ambrevar/cleanup-github-recipients ()
+  "When replying to a github message, clean up all bogus recipients.
+Also remove signature.
+This function is useful in `message-setup-hook'."
+  (interactive)
+  (let ((to (message-fetch-field "To")))
+    (when (and to
+               (string-match (rx "@reply.github.com" string-end)
+                             (cadr (mail-extract-address-components to))))
+      (dolist (hdr '("To" "Cc" "Bcc"))
+        (let ((header-value (message-fetch-field hdr)))
+          (when header-value
+            (message-replace-header
+             hdr
+             (mapconcat (lambda (addrcell)
+                          (format "\"%s\" <%s>" (car addrcell) (cadr addrcell)))
+                        (cl-delete-if
+                         (lambda (addrcell)
+                           (string-match (rx "@noreply.github.com" string-end)
+                                         (cadr addrcell)))
+                         (mail-extract-address-components  header-value t))
+                        ", ")))))
+      ;; Delete signature if any.
+      (delete-region (save-excursion
+                       (message-goto-signature)
+                       (unless (eobp)
+                         (forward-line -1))
+                       (point))
+                     (point-max))
+      ;; Deleting trailing blank lines.
+      (save-excursion
+        (goto-char (point-max))
+        (delete-blank-lines)
+        (delete-blank-lines)))))
+(add-hook 'message-setup-hook 'ambrevar/cleanup-github-recipients)
 
 
 (defvar ambrevar/message-compose-fortune-p nil