Support Spaces in Diffusion

Summary:
Ref T8493. Diffusion is probably the strongest upstream use case we have for Spaces right now, so I want to get us on it to kick the tires a bit.

Small amount of hackiness around the multi-page form thing but it shouldn't create any problems.

Test Plan:
  - Created a new repo.
  - Edited a repo.
  - Tried invalid edits, saw value preserved.
  - Viewed edit full detail screen, saw space info.
  - Viewed repo detail view, saw space.
  - Viewed repo list view, saw space.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8493

Differential Revision: https://secure.phabricator.com/D13414

src/applications/diffusion/controller/DiffusionRepositoryEditMainController.php

@@ -386,9 +386,17 @@ final class DiffusionRepositoryEditMainController
       $viewer,
       $repository);
 
+    $view_parts = array();
+    if (PhabricatorSpacesNamespaceQuery::getViewerSpacesExist($viewer)) {
+      $space_phid = PhabricatorSpacesNamespaceQuery::getObjectSpacePHID(
+        $repository);
+      $view_parts[] = $viewer->renderHandle($space_phid);
+    }
+    $view_parts[] = $descriptions[PhabricatorPolicyCapability::CAN_VIEW];
+
     $view->addProperty(
       pht('Visible To'),
-      $descriptions[PhabricatorPolicyCapability::CAN_VIEW]);
+      phutil_implode_html(" \xC2\xB7 ", $view_parts));
 
     $view->addProperty(
       pht('Editable By'),