Adding the required changes to to a subtree split of the validation library

composer.json

@@ -41,6 +41,7 @@
 	},
 	"replace": {
 		"cakephp/collection": "self.version",
-		"cakephp/event": "self.version"
+		"cakephp/event": "self.version",
+		"cakephp/validation": "self.version"
 	}
 }

src/Validation/README.md

@@ -0,0 +1,34 @@
+# CakePHP Validation Library
+
+The validation library in CakePHP provides features to build validators that can validate arbitrary
+arrays of data with ease.
+
+## Usage
+
+Validator objects define the rules that apply to a set of fields. Validator objects contain a mapping between
+fields and validation sets. Creating a validator is simple:
+
+```php
+use Cake\Validation\Validator;
+
+$validator = new Validator();
+$validator
+    ->validatePresence('email')
+    ->add('email', 'validFormat', [
+        'rule' => 'email',
+        'message' => 'E-mail must be valid'
+    ])
+    ->validatePresence('name')
+    ->notEmpty('name', 'We need your name.')
+    ->validatePresence('comment')
+    ->notEmpty('comment', 'You need to give a comment.');
+
+$errors = $validator->errors($_POST);
+if (!empty($errors)) {
+    // display errors.
+}
+```
+
+## Documentation
+
+Please make sure you check the [official documentation](http://book.cakephp.org/3.0/en/core-libraries/validation.html)

src/Validation/composer.json

@@ -0,0 +1,17 @@
+{
+	"name": "cakephp/validation",
+	"description": "CakePHP Validation library",
+	"license": "MIT",
+	"authors": [
+		{
+		"name": "CakePHP Community",
+		"homepage": "http://cakephp.org"
+	}
+	],
+	"autoload": {
+		"psr-4": {
+			"Cake\\Validation\\": "."
+		}
+	},
+	"minimum-stability": "beta"
+}