Add MakeRemoteMirrorsDisabledByDefault DB migration

db/migrate/20180508055821_make_remote_mirrors_disabled_by_default.rb

+class MakeRemoteMirrorsDisabledByDefault < ActiveRecord::Migration
+  DOWNTIME = false
+
+  def up
+    change_column_default :remote_mirrors, :enabled, false
+  end
+
+  def down
+    change_column_default :remote_mirrors, :enabled, true
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20180503200320) do
+ActiveRecord::Schema.define(version: 20180508055821) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -1712,7 +1712,7 @@ ActiveRecord::Schema.define(version: 20180503200320) do
   create_table "remote_mirrors", force: :cascade do |t|
     t.integer "project_id"
     t.string "url"
-    t.boolean "enabled", default: true
+    t.boolean "enabled", default: false
     t.string "update_status"
     t.datetime "last_update_at"
     t.datetime "last_successful_update_at"