Restore backwards compatibility with old 2.x in FormHelper.

Restore the behavior of the string 'action' option to its former glory.
While we've deprecated this it needs to continue working as it did
before.

Refs #8628

lib/Cake/Test/Case/View/Helper/FormHelperTest.php

@@ -8699,6 +8699,37 @@ public function testCreateNoUrl() {
 		$this->assertTags($result, $expected);
 	}
 
+/**
+ * Test that the action key still uses the model as the implicit controller
+ * when the url option is undefined. While the action parameter is deprecated
+ * we need it to continue working for the duration of 2.x
+ *
+ * @return void
+ */
+	public function testCreateUrlImpliedController()
+	{
+		$restore = error_reporting(E_ALL ^ E_USER_DEPRECATED);
+		$this->Form->request['controller'] = 'posts';
+		$result = $this->Form->create('Comment', array(
+			'action' => 'addComment',
+			'id' => 'addCommentForm',
+			'type' => 'POST'
+		));
+		$expected = array(
+			'form' => array(
+				'action' => '/comments/addComment',
+				'id' => 'addCommentForm',
+				'method' => 'post',
+				'accept-charset' => strtolower(Configure::read('App.encoding'))
+			),
+			'div' => array('style' => 'display:none;'),
+			'input' => array('type' => 'hidden', 'name' => '_method', 'value' => 'POST'),
+			'/div'
+		);
+		$this->assertTags($result, $expected);
+		error_reporting($restore);
+	}
+
 /**
  * Test the onsubmit option for create()
  *

lib/Cake/View/Helper/FormHelper.php

@@ -382,6 +382,7 @@ public function create($model = null, $options = array()) {
 		if (isset($options['action'])) {
 			trigger_error('Using key `action` is deprecated, use `url` directly instead.', E_USER_DEPRECATED);
 		}
+
 		if (is_array($options['url']) && isset($options['url']['action'])) {
 			$options['action'] = $options['url']['action'];
 		}
@@ -393,7 +394,7 @@ public function create($model = null, $options = array()) {
 
 		if ($options['action'] === null && $options['url'] === null) {
 			$options['action'] = $this->request->here(false);
-		} elseif (is_array($options['url'])) {
+		} elseif (empty($options['url']) || is_array($options['url'])) {
 			if (empty($options['url']['controller'])) {
 				if (!empty($model)) {
 					$options['url']['controller'] = Inflector::underscore(Inflector::pluralize($model));