set correct default validate option, now matches saveAll/saveMany default value, fixes #2492

lib/Cake/Model/Model.php

@@ -2018,8 +2018,8 @@ class Model extends Object {
  *
  * #### Options
  *
- * - `validate` Set to false to disable validation, true to validate each record before saving,
- *   'first' to validate *all* records before any are saved. Defaults to `true`.
+ * - `validate` Set to `false` to disable validation, `true` to validate each record before saving,
+ *   'first' to validate *all* records before any are saved(default),
  * - `atomic` If true (default), will attempt to save all records in a single transaction.
  *   Should be set to false if database/table does not support transactions.
  * - `fieldList` Equivalent to the $fieldList parameter in Model::save()
@@ -2036,7 +2036,7 @@ class Model extends Object {
 			$data = $this->data;
 		}
 
-		$options = array_merge(array('validate' => true, 'atomic' => true), $options);
+		$options = array_merge(array('validate' => 'first', 'atomic' => true), $options);
 		$this->validationErrors = $validationErrors = array();
 
 		if (empty($data) && $options['validate'] !== false) {

lib/Cake/Test/Case/Model/ModelWriteTest.php

@@ -4260,8 +4260,7 @@ class ModelWriteTest extends BaseModelTest {
 					'user_id' => 1
 				),
 				'Attachment' => array('attachment' => '')
-			),
-			array('validate' => 'first')
+			)
 		), false);
 		$expected = array(
 			'Comment' => array('comment' => array('This field cannot be left blank')),