get_routes_as_head

# File actionpack/lib/action_dispatch/journey/router.rb, line 150
        def get_routes_as_head(routes)
          precedence = (routes.map(&:precedence).max || 0) + 1
          routes = routes.select { |r|
            r.verb === "GET" && !(r.verb === "HEAD")
          }.map! { |r|
            Route.new(r.name,
                      r.app,
                      r.path,
                      r.conditions.merge(request_method: "HEAD"),
                      r.defaults).tap do |route|
                        route.precedence = r.precedence + precedence
                      end
          }
          routes.flatten!
          routes
        end