Explicitly degrade edge editing for commit/task edges until T4896

Summary:
Commits don't support `PhabricatorApplicationTransactionInterface` yet, so the "Edit Maniphest Tasks" dialog from the commit UI currently bombs.

Hard-code it to do the correct writes in a low-level way. After T4896 we can remove this and do `ApplicationTransaction` stuff.

Test Plan: Used the "Edit Maniphest Tasks" UI from Diffusion.

Reviewers: joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D9975

src/applications/search/controller/PhabricatorSearchAttachController.php

@@ -57,6 +57,39 @@ final class PhabricatorSearchAttachController
       $phids = array_values($phids);
 
       if ($edge_type) {
+        if ($object instanceof PhabricatorRepositoryCommit) {
+          // TODO: Remove this entire branch of special cased grossness
+          // after T4896.
+
+          $old_phids = PhabricatorEdgeQuery::loadDestinationPHIDs(
+            $this->phid,
+            $edge_type);
+          $add_phids = $phids;
+          $rem_phids = array_diff($old_phids, $add_phids);
+
+          // Doing this correctly (in a way that writes edge transactions) would
+          // be a huge mess and we don't get the commit half of the transaction
+          // anyway until T4896, so just write the edges themselves and skip
+          // the transactions for now.
+
+          $editor = new PhabricatorEdgeEditor();
+          foreach ($add_phids as $phid) {
+            $editor->addEdge(
+              $object->getPHID(),
+              DiffusionCommitHasTaskEdgeType::EDGECONST,
+              $phid);
+          }
+
+          foreach ($rem_phids as $phid) {
+            $editor->removeEdge(
+              $object->getPHID(),
+              DiffusionCommitHasTaskEdgeType::EDGECONST,
+              $phid);
+          }
+
+          $editor->save();
+
+        } else {
           if (!$object instanceof PhabricatorApplicationTransactionInterface) {
             throw new Exception(
               pht(
@@ -83,6 +116,7 @@ final class PhabricatorSearchAttachController
           $txn_editor->applyTransactions(
             $object->getApplicationTransactionObject(),
             array($txn_template));
+        }
 
         return id(new AphrontReloadResponse())->setURI($handle->getURI());
       } else {