Modernize most somewhat-weird Diffusion controllers

Summary: Ref T4245. This gets everything else except serving HTTP requests (complicated) and lint (quite weird).

Test Plan:
  - Viewed a diff.
  - Viewed externals.
  - Viewed history table to see last modified.
  - Did path completion and validation in Owners.
  - Did tree path search in Diffusion.
  - Viewed a repository.
  - Created a new repository.
  - Looked up symbols.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4245

Differential Revision: https://secure.phabricator.com/D14947

src/applications/diffusion/controller/DiffusionPathValidateController.php

@@ -2,37 +2,29 @@
 
 final class DiffusionPathValidateController extends DiffusionController {
 
-  protected function shouldLoadDiffusionRequest() {
-    return false;
+  protected function getRepositoryIdentifierFromRequest(
+    AphrontRequest $request) {
+    return $request->getStr('repositoryPHID');
   }
 
-  protected function processDiffusionRequest(AphrontRequest $request) {
-
-    $repository_phid = $request->getStr('repositoryPHID');
-    $repository = id(new PhabricatorRepositoryQuery())
-      ->setViewer($request->getUser())
-      ->withPHIDs(array($repository_phid))
-      ->executeOne();
-    if (!$repository) {
-      return new Aphront400Response();
+  public function handleRequest(AphrontRequest $request) {
+    $response = $this->loadDiffusionContext();
+    if ($response) {
+      return $response;
     }
 
+    $viewer = $this->getViewer();
+    $drequest = $this->getDiffusionRequest();
+    $repository = $drequest->getRepository();
+
     $path = $request->getStr('path');
     $path = ltrim($path, '/');
 
-    $drequest = DiffusionRequest::newFromDictionary(
-      array(
-        'user' => $request->getUser(),
-        'repository' => $repository,
-        'path' => $path,
-      ));
-    $this->setDiffusionRequest($drequest);
-
     $browse_results = DiffusionBrowseResultSet::newFromConduit(
       $this->callConduitWithDiffusionRequest(
         'diffusion.browsequery',
         array(
-          'path' => $drequest->getPath(),
+          'path' => $path,
           'commit' => $drequest->getCommit(),
           'needValidityOnly' => true,
         )));