Merge branch '4.4' into 5.0

* 4.4:
  [#13000] Fixed newline
  Update testing.rst
  [#12722] Added filename comment to avoid confusion
  Update micro_kernel_trait.rst
  Update broken links

Author: wouterj

configuration/micro_kernel_trait.rst

@@ -22,6 +22,7 @@ via Composer:
 
 Next, create an ``index.php`` file that defines the kernel class and executes it::
 
+    // index.php
     use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
     use Symfony\Component\Config\Loader\LoaderInterface;
     use Symfony\Component\DependencyInjection\ContainerBuilder;

testing.rst

@@ -545,6 +545,8 @@ allows fetching both public and all non-removed private services::
 
     // gives access to the same services used in your test, unless you're using
     // $client->insulate() or using real HTTP requests to test your application
+    // don't forget to call self::bootKernel() before, otherwise, the container
+    // will be empty
     $container = self::$container;
 
 For a list of services available in your application, use the ``debug:container``