add beforeEnqueue hook that allows the enqueue to be cancelled

lib/Resque/Job.php

@@ -50,14 +50,17 @@ class Resque_Job
 	 *
 	 * @return string
 	 */
-	public static function create($queue, $class, $args = null, $monitor = false)
+	public static function create($queue, $class, $args = null, $monitor = false, $id = null)
 	{
+		if (is_null($id)) {
+			$id = Resque::generateJobId();
+		}
+
 		if($args !== null && !is_array($args)) {
 			throw new InvalidArgumentException(
 				'Supplied $args must be an array.'
 			);
 		}
-		$id = md5(uniqid('', true));
 		Resque::push($queue, array(
 			'class'	=> $class,
 			'args'	=> array($args),

lib/Resque/Job/DontCreate.php

@@ -0,0 +1,12 @@
+<?php
+/**
+ * Exception to be thrown if while enqueuing a job it should not be created.
+ *
+ * @package		Resque/Job
+ * @author		Chris Boulton <chris@bigcommerce.com>
+ * @license		http://www.opensource.org/licenses/mit-license.php
+ */
+class Resque_Job_DontCreate extends Exception
+{
+
+}