Hide revision content if author has not signed required legal documents

Summary: Fixes T7446.

Test Plan: {F333301}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7446

Differential Revision: https://secure.phabricator.com/D12021

src/applications/differential/controller/DifferentialRevisionViewController.php

@@ -422,17 +422,43 @@ final class DifferentialRevisionViewController extends DifferentialController {
 
     $page_pane = id(new DifferentialPrimaryPaneView())
       ->setID($pane_id)
-      ->appendChild(array(
-        $comment_view,
-        $diff_history,
-        $warning,
-        $local_view,
-        $toc_view,
-        $other_view,
-        $changeset_view,
-      ));
-    if ($comment_form) {
+      ->appendChild($comment_view);
 
+    $signatures = DifferentialRequiredSignaturesField::loadForRevision(
+      $revision);
+    $missing_signatures = false;
+    foreach ($signatures as $phid => $signed) {
+      if (!$signed) {
+        $missing_signatures = true;
+      }
+    }
+
+    if ($missing_signatures) {
+      $signature_message = id(new PHUIInfoView())
+        ->setErrors(
+          array(
+            array(
+              phutil_tag('strong', array(), pht('Content Hidden:')),
+              ' ',
+              pht(
+                'The content of this revision is hidden until the author has '.
+                'signed all of the required legal agreements.'),
+            ),
+          ));
+      $page_pane->appendChild($signature_message);
+    } else {
+      $page_pane->appendChild(
+        array(
+          $diff_history,
+          $warning,
+          $local_view,
+          $toc_view,
+          $other_view,
+          $changeset_view,
+        ));
+    }
+
+    if ($comment_form) {
       $page_pane->appendChild($comment_form);
     } else {
       // TODO: For now, just use this to get "Login to Comment".

src/docs/user/userguide/legalpad.diviner

@@ -56,6 +56,10 @@ After you've done this, all new reviews created in Differential by authors who
 have not signed the document will trigger a signature requirement. These reviews
 can not be accepted until the document has been signed.
 
+The content of these revisions will also be hidden until the document has been
+signed. This prevents reviewers from being tainted by examining the changes if
+the author ultimately declines to sign the CLA.
+
 If the author has already signed all of the required documents, Herald will not
 take any actions. This reduces the amount of noise the CLA process generates for
 regular contributors.