set_migration_assigns!

# File railties/lib/rails/generators/migration.rb, line 37
      def set_migration_assigns!(destination)
        destination = File.expand_path(destination, self.destination_root)

        migration_dir = File.dirname(destination)
        @migration_number     = self.class.next_migration_number(migration_dir)
        @migration_file_name  = File.basename(destination, '.rb')
        @migration_class_name = @migration_file_name.camelize
      end