Fix Phriction document previews for the root document ("/") with Apache option "MergeSlashes On"

Summary:
Ref T13662. I ran into this while trying to reproduce the mention issue discussed there.

Currently, the root document (with slug "/") attempts to preview using the URI `/phriction/preview//` (with two `//` at the end). This is collapsed into "/phriction/preview/" by Apache if "MergeSlashes On" is configured, which is the default behavior. The route then 404s.

Instead, just use "/phriction/preview/?slug=/" so this endpoint functions properly regardless of the "MergeSlashes" configuration.

Test Plan:
  - Configured Apache with "MergeSlashes On" (which is the default behavior).
  - Tried to preview a content edit of the root document in Phriction, which didn't work and generated 404s for "/phriction/preview//" in the console log.
  - Applied patch.
  - Previwed content in Phriction (which now worked properly).
  - Accessed `/a//b///c////` and similar with "MergeSlashes On" and "MergeSlashes Off", confirmed that this option controls whether PHP receives a URI with or without merged slashes in "__path__" after rewriting.

Reviewers: 0

Reviewed By: 0

Maniphest Tasks: T13662

Differential Revision: https://secure.phabricator.com/D21708

src/applications/phriction/application/PhabricatorPhrictionApplication.php

@@ -61,7 +61,7 @@ final class PhabricatorPhrictionApplication extends PhabricatorApplication {
         'new/'                        => 'PhrictionNewController',
         'move/(?P<id>[1-9]\d*)/' => 'PhrictionMoveController',
 
-        'preview/(?P<slug>.*/)' => 'PhrictionMarkupPreviewController',
+        'preview/' => 'PhrictionMarkupPreviewController',
         'diff/(?P<id>[1-9]\d*)/' => 'PhrictionDiffController',
 
         $this->getEditRoutePattern('document/edit/')

src/applications/phriction/controller/PhrictionEditController.php

@@ -316,9 +316,17 @@ final class PhrictionEditController
       ->setBackground(PHUIObjectBoxView::WHITE_CONFIG)
       ->setForm($form);
 
+    $preview_uri = '/phriction/preview/';
+    $preview_uri = new PhutilURI(
+      $preview_uri,
+      array(
+        'slug' => $document->getSlug(),
+      ));
+    $preview_uri = phutil_string_cast($preview_uri);
+
     $preview = id(new PHUIRemarkupPreviewPanel())
       ->setHeader($content->getTitle())
-      ->setPreviewURI('/phriction/preview/'.$document->getSlug())
+      ->setPreviewURI($preview_uri)
       ->setControlID('document-textarea')
       ->setPreviewType(PHUIRemarkupPreviewPanel::DOCUMENT);
 

src/applications/phriction/controller/PhrictionMarkupPreviewController.php

@@ -8,7 +8,7 @@ final class PhrictionMarkupPreviewController
     $viewer = $request->getUser();
 
     $text = $request->getStr('text');
-    $slug = $request->getURIData('slug');
+    $slug = $request->getStr('slug');
 
     $output = PhabricatorMarkupEngine::renderOneObject(
       id(new PhabricatorMarkupOneOff())