emacs: add function to resend message to new recipients

The new function notmuch-show-message-resend re-sends
message to new recipients using #'message-resend.

Recipients are read from minibuffer as a comma-separated
string (with some keyboard support including tab completion).

Final confirmation before sending is asked.

emacs/notmuch-address.el

@@ -249,6 +249,25 @@ called when harvesting finishes."
 
 ;;
 
+(defun notmuch-address-from-minibuffer (prompt)
+  (if (not notmuch-address-command)
+      (read-string prompt)
+    (let ((rmap (copy-keymap minibuffer-local-map))
+	  (omap minibuffer-local-map))
+      ;; Configure TAB to start completion when executing read-string.
+      ;; "Original" minibuffer keymap is restored just before calling
+      ;; notmuch-address-expand-name as it may also use minibuffer-local-map
+      ;; (completing-read probably does not but if something else is used there).
+      (define-key rmap (kbd "TAB") (lambda ()
+				     (interactive)
+				     (let ((enable-recursive-minibuffers t)
+					   (minibuffer-local-map omap))
+				       (notmuch-address-expand-name))))
+      (let ((minibuffer-local-map rmap))
+	(read-string prompt)))))
+
+;;
+
 (provide 'notmuch-address)
 
 ;;; notmuch-address.el ends here

emacs/notmuch-show.el

@@ -1855,6 +1855,14 @@ any effects from previous calls to
       (error "No open messages to forward."))
     (notmuch-mua-new-forward-messages open-messages prompt-for-sender)))
 
+(defun notmuch-show-resend-message (addresses)
+  "Resend the current message."
+  (interactive (list (notmuch-address-from-minibuffer "Resend to: ")))
+  (when (y-or-n-p (concat "Confirm resend to " addresses " "))
+    (notmuch-show-view-raw-message)
+    (message-resend addresses)
+    (notmuch-bury-or-kill-this-buffer)))
+
 (defun notmuch-show-next-message (&optional pop-at-end)
   "Show the next message.