Fix security.require-https by marking redirect as external

Summary:
Resolves T5937.  HTTPS redirects caused by `security.require-https` use a full scheme, domain and port in the URI.  Consequently, this causes invocation of the new external redirect logic and prevents redirection from occurring properly when accessing the HTTP version of Phabricator that has `security.require-https` turned on.

I've also fixed the automatic slash redirection logic to add the external flag where appropriate.

Test Plan: Configured SSL on my local machine and turned on `security.require-https`.  Observed the "Refusing to redirect" exception on master, while the redirect completed successfully with this patch.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T5937

Differential Revision: https://secure.phabricator.com/D10318

src/aphront/configuration/AphrontApplicationConfiguration.php

@@ -14,7 +14,7 @@ abstract class AphrontApplicationConfiguration {
   abstract public function getURIMap();
   abstract public function buildRequest();
   abstract public function build404Controller();
-  abstract public function buildRedirectController($uri);
+  abstract public function buildRedirectController($uri, $external);
 
   final public function setRequest(AphrontRequest $request) {
     $this->request = $request;
@@ -96,7 +96,10 @@ abstract class AphrontApplicationConfiguration {
         $https_uri = $request->getRequestURI();
         $https_uri->setDomain($request->getHost());
         $https_uri->setProtocol('https');
-        return $this->buildRedirectController($https_uri);
+
+        // In this scenario, we'll be redirecting to HTTPS using an absolute
+        // URI, so we need to permit an external redirect.
+        return $this->buildRedirectController($https_uri, true);
       }
     }
 
@@ -188,7 +191,9 @@ abstract class AphrontApplicationConfiguration {
 
         if ($controller && !$request->isHTTPPost()) {
           $slash_uri = $request->getRequestURI()->setPath($path.'/');
-          return $this->buildRedirectController($slash_uri);
+
+          $external = strlen($request->getRequestURI()->getDomain());
+          return $this->buildRedirectController($slash_uri, $external);
         }
       }
       return $this->build404Controller();