Slightly modernize all Diffusion edit endpoints

Summary: Ref T4245. Prepares edit endpoints for more flexible repository identifiers.

Test Plan:
  - Added, edited, deleted mirror.
  - Created repository.
  - Edited basic repository information.
  - Edited policies for a repository.
  - Activated/deactivated repository.
  - Updated a repository.
  - Hit "Delete" dialog for a repository.
  - Edited hosting.
  - Toggled dangerous changes.
  - Edited branches.
  - Edited automation.
  - Tested automation.
  - Edited storage.
  - Edited staging.
  - Edited encoding.
  - Edited symbols.
  - Edited branches.
  - Edited actions.
  - Tried to do edits as an unprivileged user.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4245

Differential Revision: https://secure.phabricator.com/D14945

src/applications/diffusion/controller/DiffusionRepositoryEditMainController.php

@@ -3,15 +3,15 @@
 final class DiffusionRepositoryEditMainController
   extends DiffusionRepositoryEditController {
 
-  protected function processDiffusionRequest(AphrontRequest $request) {
-    $viewer = $request->getUser();
-    $drequest = $this->diffusionRequest;
-    $repository = $drequest->getRepository();
+  public function handleRequest(AphrontRequest $request) {
+    $response = $this->loadDiffusionContextForEdit();
+    if ($response) {
+      return $response;
+    }
 
-    PhabricatorPolicyFilter::requireCapability(
-      $viewer,
-      $repository,
-      PhabricatorPolicyCapability::CAN_EDIT);
+    $viewer = $this->getViewer();
+    $drequest = $this->getDiffusionRequest();
+    $repository = $drequest->getRepository();
 
     $is_svn = false;
     $is_git = false;