Set "importing" flag on repositories created via API

Summary: Ref T6516. We incorrectly fail to set this flag on repositories created via Conduit, which activates too many actions on old commits.

Test Plan:
  - Created a new repository via Conduit, verified it was "importing" after creation.
  - Created a new repostiory via web UI, verified it was "importing" after creation.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T6516

Differential Revision: https://secure.phabricator.com/D11964

src/applications/diffusion/controller/DiffusionRepositoryCreateController.php

@@ -152,10 +152,6 @@ final class DiffusionRepositoryCreateController
           // transactions to apply this change.
           $repository->setCallsign($callsign);
 
-          // Put the repository in "Importing" mode until we finish
-          // parsing it.
-          $repository->setDetail('importing', true);
-
           $xactions[] = id(clone $template)
             ->setTransactionType($type_name)
             ->setNewValue(