def submit(value = nil, options = {})
      value = (@object.new_record?? "Create" : "Update") if value.nil?
      build_shell(value, options, 'submit_button') { super }
    end
def submit(value = nil, options = {})
      value = (@object.new_record?? "Create" : "Update") if value.nil?
      build_shell(value, options, 'submit_button') { super }
    end
Submit button with smart default text (if +value+ is nil uses "Create"
 for new record or "Update" for old record).