Squashed commit of the following:

commit a603c51aa5bdfeb431f7e9e5ccfbd25ecb05e083
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Thu Nov 16 18:41:19 2017 +0900

    Add environment_scope to cluster table

db/migrate/20171116135628_add_environment_scope_to_clusters.rb

+class AddEnvironmentScopeToClusters < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_column_with_default(:clusters, :environment_scope, :string, default: '*')
+  end
+
+  def down
+    remove_column(:clusters, :environment_scope)
+  end
+end

db/schema.rb

@@ -615,6 +615,7 @@ ActiveRecord::Schema.define(version: 20171120145444) do
     t.datetime "updated_at", null: false
     t.boolean "enabled", default: true
     t.string "name", null: false
+    t.string "environment_scope", default: "*", null: false
   end
 
   add_index "clusters", ["enabled"], name: "index_clusters_on_enabled", using: :btree