[Security][HttpFoundation] splits Request::hasSession() into hasSession(), and hasPreviousSession()

This closes #774, and fixes #772.

UPDATE.md

@@ -120,6 +120,10 @@ beta1 to beta2
           'allow_add' => true,
           'allow_delete' => true,
       ));
+      
+* Request::hasSession() has been renamed to Request::hasPreviousSession(). The
+  method hasSession() still exists, but only checks if the request contains a
+  session object, not if the session was started in a previous request.
 
 PR12 to beta1
 -------------

src/Symfony/Bundle/FrameworkBundle/RequestListener.php

@@ -67,7 +67,7 @@ class RequestListener
         }
 
         // starts the session if a session cookie already exists in the request...
-        if ($request->hasSession()) {
+        if ($request->hasPreviousSession()) {
             $request->getSession()->start();
         }
     }

src/Symfony/Component/HttpFoundation/Request.php

@@ -308,12 +308,28 @@ class Request
         return $this->session;
     }
 
-    public function hasSession()
+    /**
+     * Whether the request contains a Session which was started in one of the
+     * previous requests.
+     *
+     * @return boolean
+     */
+    public function hasPreviousSession()
     {
         // the check for $this->session avoids malicious users trying to fake a session cookie with proper name
         return $this->cookies->has(session_name()) && null !== $this->session;
     }
 
+    /**
+     * Whether the request contains a Session object.
+     *
+     * @return boolean
+     */
+    public function hasSession()
+    {
+        return null !== $this->session;
+    }
+
     public function setSession(Session $session)
     {
         $this->session = $session;

src/Symfony/Component/Security/Http/Firewall/ContextListener.php

@@ -62,7 +62,7 @@ class ContextListener implements ListenerInterface
     {
         $request = $event->getRequest();
 
-        $session = $request->hasSession() ? $request->getSession() : null;
+        $session = $request->hasPreviousSession() ? $request->getSession() : null;
 
         if (null === $session || null === $token = $session->get('_security_'.$this->contextKey)) {
             $this->context->setToken(null);