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/DiffusionMirrorEditController.php

@@ -117,17 +117,13 @@ final class DiffusionMirrorEditController
           ->setError($e_credentials)
           ->setOptions($credentials));
 
-    $dialog = id(new AphrontDialogView())
-      ->setUser($viewer)
+    return $this->newDialog()
       ->setTitle($title)
       ->setWidth(AphrontDialogView::WIDTH_FORM)
       ->appendChild($form_errors)
       ->appendChild($form)
       ->addSubmitButton($submit)
       ->addCancelButton($edit_uri);
-
-    return id(new AphrontDialogResponse())
-      ->setDialog($dialog);
   }