FEATURE: allow moderators to globally pin topics

db/migrate/20140407055830_add_pinned_globally_to_topics.rb

@@ -0,0 +1,12 @@
+class AddPinnedGloballyToTopics < ActiveRecord::Migration
+  def up
+    add_column :topics, :pinned_globally, :boolean, null: false, default: false
+    execute "UPDATE topics set pinned_globally = 't' where category_id = (
+      SELECT value::int FROM site_settings WHERE name = 'uncategorized_category_id') AND pinned_at IS NOT NULL
+    "
+  end
+
+  def down
+    remove_column :topics, :pinned_globally
+  end
+end