Fix an issue with paginating queries which reverse vector ordering components

Summary:
Ref T10188. If you issue certain queries which use reverse ordering (like "All tasks, oldest update to newest update") and then try to page forward, we build the paging clause without reversing the column order correctly.

For example, the ordering of "oldest update to newest update" is "dateModified ASC, id ASC", so the second page should include an "id > X" query. Currently, this builds as "id < X" incorrectly instead.

The cause of this is just a failure to re-reverse a reversing flag when constructing the paging clause.

Test Plan:
  - Queried tasks by update, oldest to newest, with no grouping, etc.
  - Paged to second page.
  - After change, got a valid second page with a good query in the Services tab.
  - Made some other normal queries.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10188

Differential Revision: https://secure.phabricator.com/D15076

src/infrastructure/query/policy/PhabricatorCursorPagedPolicyAwareQuery.php

@@ -381,6 +381,12 @@ abstract class PhabricatorCursorPagedPolicyAwareQuery
       $column = $orderable[$key];
       $column['value'] = $value_map[$key];
 
+      // If the vector component is reversed, we need to reverse whatever the
+      // order of the column is.
+      if ($order->getIsReversed()) {
+        $column['reverse'] = !idx($column, 'reverse', false);
+      }
+
       $columns[] = $column;
     }