Provide more UI guidance when creating repositories

Summary: Ref T10923. Walk users through the "create, configure, activate" workflow a little better and set expectations more clearly.

Test Plan:
  - Created a new repository, saw new UI help.
  - Activated repository, saw onboarding help disappear.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10923

Differential Revision: https://secure.phabricator.com/D15875

src/applications/diffusion/editor/DiffusionRepositoryEditEngine.php

@@ -40,6 +40,8 @@ final class DiffusionRepositoryEditEngine
     $viewer = $this->getViewer();
     $repository = PhabricatorRepository::initializeNewRepository($viewer);
 
+    $repository->setDetail('newly-initialized', true);
+
     $vcs = $this->getVersionControlSystem();
     if ($vcs) {
       $repository->setVersionControlSystem($vcs);