rollback.rb

def rollback(migrations_path)
  migrations_paths_was = ActiveRecord::Migrator.migrations_paths
  ActiveRecord::Migrator.migrations_paths = [migrations_path]
  ActiveRecord::Tasks::DatabaseTasks.check_target_version

  scope = ENV["SCOPE"]
  verbose_was, ActiveRecord::Migration.verbose = ActiveRecord::Migration.verbose, ActiveRecord::Tasks::DatabaseTasks.send(:verbose?)

  ActiveRecord::Base.connection.migration_context.down(ActiveRecord::Tasks::DatabaseTasks.target_version) do |migration|
    scope.blank? || scope == migration.scope
  end

  ActiveRecord::Base.clear_cache!
ensure
  ActiveRecord::Migrator.migrations_paths = migrations_paths_was - [migrations_path]
  ActiveRecord::Migration.verbose = verbose_was
end