Documented info method

Author: wouterj

components/config/definition.rst

@@ -287,6 +287,19 @@ has a certain value:
         ->end()
     ;
 
+Documenting the Option
+----------------------
+
+All options can be documented using the
+:method:`Symfony\\Component\\Config\\Definition\\Builder\\NodeDefinition::info`
+method.
+
+The info will be printed as a comment when dumping the configuration tree.
+
+.. versionadded:: 2.6
+    Since Symfony 2.6, the info will also be added to the exception message
+    when an invalid type is given.
+
 Optional Sections
 -----------------