mu4e: Add -kill-ring-save-message-id function

.emacs.d/lisp/init-mu4e.el

@@ -326,4 +326,10 @@ Addresses in `mu4e-user-mail-address-list' are skipped."
 :EMAIL: %(ambrevar/org-contacts-template-email)
 :END:")))
 
+(defun ambrevar/mu4e-kill-ring-save-message-id (&optional msg)
+  "Save MSG's \"message-id\" field to the kill-ring.
+If MSG is nil, use message at point."
+  (interactive)
+  (kill-new (mu4e-message-field (or msg (mu4e-message-at-point)) :message-id)))
+
 (provide 'init-mu4e)