Merge branch '2.8' into 3.0

* 2.8:
  #17676 - making the proxy instantiation compatible with ProxyManager 2.x by detecting proxy features
  Fix bug when using an private aliased factory service
  ChoiceFormField of type "select" could be "disabled"
  Update contributing docs
  [Console] Fix escaping of trailing backslashes
  Fix constraint validator alias being required
  [ci] clone with depth=1 to kill push-forced PRs
  Add check on If-Range header

Author: fabpot

Tests/Compiler/ReplaceAliasByActualDefinitionPassTest.php

@@ -16,6 +16,8 @@
 use Symfony\Component\DependencyInjection\Definition;
 use Symfony\Component\DependencyInjection\Reference;
 
+require_once __DIR__.'/../Fixtures/includes/foo.php';
+
 class ReplaceAliasByActualDefinitionPassTest extends \PHPUnit_Framework_TestCase
 {
     public function testProcess()
@@ -46,6 +48,26 @@ public function testProcess()
         $this->assertSame('b_alias', (string) $resolvedFactory[0]);
     }
 
+    /**
+     * @group legacy
+     */
+    public function testPrivateAliasesInFactory()
+    {
+        $container = new ContainerBuilder();
+
+        $container->register('a', 'FooClass');
+        $container->register('b', 'FooClass')
+            ->setFactoryService('a')
+            ->setFactoryMethod('getInstance');
+
+        $container->register('c', 'stdClass')->setPublic(false);
+        $container->setAlias('c_alias', 'c');
+
+        $this->process($container);
+
+        $this->assertInstanceOf('FooClass', $container->get('b'));
+    }
+
     /**
      * @expectedException \InvalidArgumentException
      */