Fix differential.getdiff, etc., for diffs with no Arcanist Project

Summary:
`getArcanistProjectName()` has some logic which gets messy with the `self::ATTACHABLE` mechanism. This makes `differential.getdiff` and similar Conduit methods throw an exception when querying a diff which doesn't have a project. See <http://pastebin.com/Czzrd0Jz>.

Instead, unconditionally attach a project (possibly `null`) when loading diffs if they need projects.

Test Plan: Ran `differential.getdiff` against a `arc diff --raw` diff with no project, got a result instead of an exception.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran, sttwister

Differential Revision: https://secure.phabricator.com/D7101

src/applications/differential/query/DifferentialDiffQuery.php

@@ -77,13 +77,16 @@ final class DifferentialDiffQuery
           'phid IN (%Ls)',
           $phids);
       $project_map = mpull($projects, null, 'getPHID');
-      foreach ($diffs as $diff) {
-        if ($diff->getArcanistProjectPHID()) {
-          $project = $project_map[$diff->getArcanistProjectPHID()];
-          $diff->attachArcanistProject($project);
-        }
-      }
     }
+
+    foreach ($diffs as $diff) {
+      $project = null;
+      if ($diff->getArcanistProjectPHID()) {
+        $project = idx($project_map, $diff->getArcanistProjectPHID());
+      }
+      $diff->attachArcanistProject($project);
+    }
+
     return $diffs;
   }
 

src/applications/differential/storage/DifferentialDiff.php

@@ -62,7 +62,7 @@ final class DifferentialDiff
   }
 
   public function attachArcanistProject(
-    PhabricatorRepositoryArcanistProject $project) {
+    PhabricatorRepositoryArcanistProject $project = null) {
     $this->arcanistProject = $project;
     return $this;
   }