org-notify.el: Limit the number of notifications

(org-notify-max-notifications-per-run): New option for limiting the
notifications.
(org-notify-process): Use it.

contrib/lisp/org-notify.el

@@ -74,6 +74,11 @@
   :type 'boolean
   :group 'org-notify)
 
+(defcustom org-notify-max-notifications-per-run 3
+  "Maximum number of notifications per run of `org-notify-process'."
+  :type 'integer
+  :group 'org-notify)
+
 (defconst org-notify-actions
   '("show" "show" "done" "done" "hour" "one hour later" "day" "one day later"
     "week" "one week later")
@@ -158,6 +163,7 @@ PERIOD."
 (cl-defun org-notify-process ()
   "Process the todo-list, and possibly notify user about upcoming or
 forgotten tasks."
+  (let ((notification-cnt 0))
     (cl-macrolet ((prm (k) `(plist-get prms ,k))  (td (k) `(plist-get todo ,k)))
       (dolist (todo (org-notify-todo-list))
 	(let* ((deadline (td :deadline))  (heading (td :heading))
@@ -179,12 +185,15 @@ forgotten tasks."
                       (ding))
                   (unless (listp actions)
                     (setq actions (list actions)))
+		  (cl-incf notification-cnt)
                   (dolist (action actions)
                     (funcall (if (fboundp action) action
                                (intern (concat "org-notify-action"
                                                (symbol-name action))))
-                           plist))))
-            (cl-return)))))))
+			     plist))
+		  (when (>= notification-cnt org-notify-max-notifications-per-run)
+		    (cl-return-from org-notify-process)))
+		(cl-return)))))))))
 
 (defun org-notify-add (name &rest params)
   "Add a new notification type.