Add alert category (#37)

* Added alert :category support

* Renamed var to org-alert-notification-category; added readme

README.md

@@ -118,6 +118,14 @@ variable. Use this if you'd like to customize the display of org
 notifications when using a daemon such as
 [dunst](https://github.com/knopwob/dunst).
 
+### Custom categories
+
+org-alert uses the category `'org-alert` by default. You can set this to
+something else by changing the `org-alert-notification-category`
+variable. Use this if you'd like to customize the display of org
+notifications when using a notification function that supports
+distinct categories via the `alert` `:category` property.
+
 ### Custom regexp for searching agenda entries
 
 org-alert searches for agenda entries with 'Sched' or 'Deadline' word

org-alert.el

@@ -67,6 +67,11 @@ is used to extract the time")
   "REMINDERN"
   "org property used to set a custom cutoff for an individual entry")
 
+(defvar org-alert-notification-category
+  'org-alert
+  "The symbol to pass to alert as the :category property, in order
+to allow differentiation from other uses of alert")
+
 (defun org-alert--read-subtree ()
   "Return the current subtree as a string. Adapted from
 `org-copy-subtree` from org-mode."
@@ -151,8 +156,11 @@ heading, the scheduled/deadline time, and the cutoff to apply"
       (cl-destructuring-bind (head time cutoff) entry
 	(if time
 	    (when (org-alert--check-time time cutoff)
-	      (alert (concat time ": " head) :title org-alert-notification-title))
-	  (alert head :title org-alert-notification-title))))))
+	      (alert (concat time ": " head)
+                     :title org-alert-notification-title
+                     :category org-alert-notification-category))
+	  (alert head :title org-alert-notification-title
+                 :category org-alert-notification-category))))))
 
 (defun org-alert-check ()
   "Check for active, due deadlines and initiate notifications."