Add a "refs" table to Diffusion

Summary:
Ref T7100. When a user navigates to a branch like "default" which is ambiguous:

  - don't fatal;
  - choose one alternative to resolve it to (currently more or less at random);
  - sometimes show what we did in the UI.

Also, add a new table to show the alternatives.

This will get refined in followup changes.

Test Plan:
{F384335}

{F384336}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7100

Differential Revision: https://secure.phabricator.com/D12547

src/applications/diffusion/controller/DiffusionRepositoryController.php

@@ -303,10 +303,40 @@ final class DiffusionRepositoryController extends DiffusionController {
 
     $view->setActionList($actions);
 
-    return id(new PHUIObjectBoxView())
+    $box = id(new PHUIObjectBoxView())
       ->setHeader($header)
       ->addPropertyList($view);
 
+    $info = null;
+    $drequest = $this->getDiffusionRequest();
+    if ($drequest->getRefAlternatives()) {
+      $message = array(
+        pht(
+          'The ref "%s" is ambiguous in this repository.',
+          $drequest->getBranch()),
+        ' ',
+        phutil_tag(
+          'a',
+          array(
+            'href' => $drequest->generateURI(
+              array(
+                'action' => 'refs',
+              )),
+          ),
+          pht('View Alternatives')),
+      );
+
+      $messages = array($message);
+
+      $info = id(new PHUIInfoView())
+        ->setSeverity(PHUIInfoView::SEVERITY_WARNING)
+        ->setErrors(array($message));
+
+      $box->setInfoView($info);
+    }
+
+
+    return $box;
   }
 
   private function buildBranchListTable(DiffusionRequest $drequest) {