Return Diffusion diffs through Files, not directly over Conduit

Summary:
Fixes T10423. Ref T11524. This changes `diffusion.rawdiffquery` to return a file PHID instead of a blob of data.

This is better in general, but particularly better for huge diffs (as in T10423) and diffs with non-utf8 data (as in T10423).

Test Plan:
  - Used `bin/differential extract` to extract a latin1 diff, got a clean diff.
  - Used `bin/repository reparse --herald` to rerun herald on a latin1 diff, got a clean result.
  - Pushed latin1 diffs to test commit hooks.
  - Triggered the the too large / too slow logic.
  - Viewed latin1 diffs in Diffusion.
  - Used "blame past this change" in Diffusion to hit the `before` logic.

Reviewers: chad

Reviewed By: chad

Subscribers: eadler

Maniphest Tasks: T10423, T11524

Differential Revision: https://secure.phabricator.com/D16460

src/applications/diffusion/query/rawdiff/DiffusionMercurialRawDiffQuery.php

@@ -2,11 +2,7 @@
 
 final class DiffusionMercurialRawDiffQuery extends DiffusionRawDiffQuery {
 
-  protected function executeQuery() {
-    return $this->executeRawDiffCommand();
-  }
-
-  protected function executeRawDiffCommand() {
+  protected function newQueryFuture() {
     $drequest = $this->getRequest();
     $repository = $drequest->getRepository();
 
@@ -30,11 +26,7 @@ final class DiffusionMercurialRawDiffQuery extends DiffusionRawDiffQuery {
       $commit,
       $path);
 
-    $this->configureFuture($future);
-
-    list($raw_diff) = $future->resolvex();
-
-    return $raw_diff;
+    return $future;
   }
 
 }