adding setExtensions() to allow adding more extensions as parseExtensions would override existing valid extensions

lib/Cake/Routing/Router.php

@@ -1102,13 +1102,14 @@ class Router {
 	public static function parseExtensions() {
 		self::$_parseExtensions = true;
 		if (func_num_args() > 0) {
-			self::$_validExtensions = func_get_args();
+			self::setExtensions(func_get_args(), false);
 		}
 	}
 
 /**
- * Get the list of extensions that can be parsed by Router.  To add more
- * extensions use Router::parseExtensions()
+ * Get the list of extensions that can be parsed by Router.
+ * To initially set extensions use `Router::parseExtensions()`
+ * To add more see `setExtensions()`
  *
  * @return array Array of extensions Router is configured to parse.
  */
@@ -1116,6 +1117,24 @@ class Router {
 		return self::$_validExtensions;
 	}
 
+/**
+ * Set/add valid extensions.
+ * To have the extensions parsed you still need to call `Router::parseExtensions()`
+ *
+ * @param array $extensions List of extensions to be added as valid extension
+ * @param boolean $merge Default true will merge extensions. Set to false to override current extensions
+ * @return array
+ */
+	public static function setExtensions($extensions, $merge = true) {
+		if (!is_array($extensions)) {
+			return self::$_validExtensions;
+		}
+		if (!$merge) {
+			return self::$_validExtensions = $extensions;
+		}
+		return self::$_validExtensions = array_merge(self::$_validExtensions, $extensions);
+	}
+
 }
 
 //Save the initial state

lib/Cake/Test/Case/Routing/RouterTest.php

@@ -1235,15 +1235,46 @@ class RouterTest extends CakeTestCase {
 	}
 
 /**
- * testExtensionParsingSetting method
+ * testParseExtensions method
  *
  * @return void
  */
-	public function testExtensionParsingSetting() {
+	public function testParseExtensions() {
 		$this->assertEquals(array(), Router::extensions());
 
 		Router::parseExtensions('rss');
-		$this->assertEquals(Router::extensions(), array('rss'));
+		$this->assertEquals(array('rss'), Router::extensions());
+	}
+
+/**
+ * testSetExtensions method
+ *
+ * @return void
+ */
+	public function testSetExtensions() {
+		Router::setExtensions(array('rss'));
+		$this->assertEquals(array('rss'), Router::extensions());
+
+		require CAKE . 'Config' . DS . 'routes.php';
+		$result = Router::parse('/posts.rss');
+		$this->assertFalse(isset($result['ext']));
+
+		Router::parseExtensions();
+		$result = Router::parse('/posts.rss');
+		$this->assertEquals('rss', $result['ext']);
+
+		$result = Router::parse('/posts.xml');
+		$this->assertFalse(isset($result['ext']));
+
+		Router::setExtensions(array('xml'));
+		$result = Router::extensions();
+		$this->assertEquals(array('rss', 'xml'), $result);
+
+		$result = Router::parse('/posts.xml');
+		$this->assertEquals('xml', $result['ext']);
+
+		$result = Router::setExtensions(array('pdf'), false);
+		$this->assertEquals(array('pdf'), $result);
 	}
 
 /**