Updates existing SystemHooks associated with GeoNodes to use new hook.

db/migrate/20170505133904_update_geo_nodes_system_hooks.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class UpdateGeoNodesSystemHooks < ActiveRecord::Migration
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  def up
+    attrs = {
+      push_events: false,
+      tag_push_events: false,
+      repository_update_events: true
+    }
+    SystemHook.joins('INNER JOIN "geo_nodes" ON "geo_nodes".system_hook_id = "web_hooks".id').update_all(attrs)
+  end
+
+  def down
+    attrs = {
+      push_events: true,
+      tag_push_events: true,
+      repository_update_events: false
+    }
+    SystemHook.joins('INNER JOIN "geo_nodes" ON "geo_nodes".system_hook_id = "web_hooks".id').update_all(attrs)
+  end
+end