Shopify Script - X% off sitewide

total = Input.cart.subtotal_price_was
discount = 0.2 #discount percent in decimal format
message = "20% off Sitewide" #message to show when discount is applied

Input.cart.line_items.each do |line_item|
  product = line_item.variant.product
  next if product.gift_card?
  line_item.change_line_price(line_item.line_price * (1-discount), message: message) unless discount == 0
end

Output.cart = Input.cart