Update old changesets to subscribe the creator

db/migrate/20150111192335_subscribe_old_changesets.rb

@@ -0,0 +1,10 @@
+class SubscribeOldChangesets < ActiveRecord::Migration
+  def up
+    Changeset.find_each do |changeset|
+      changeset.subscribers << changeset.user unless changeset.subscribers.exists?(changeset.user)
+    end
+  end
+
+  def down
+  end
+end