Fix HEAD response header for brid.gy

lib/adamantium/middleware/header_fix.rb

@@ -0,0 +1,24 @@
+require "rack"
+require "rack/contrib"
+
+module Adamantium
+  module Middleware
+    class HeaderFix
+      HEADERS_KLASS = Rack.release < "3" ? Rack::Utils::HeaderHash : Rack::Headers
+      private_constant :HEADERS_KLASS
+
+      def initialize(app, &block)
+        @app = app
+        @block = block
+      end
+
+      def call(env)
+        response = @app.call(env)
+        headers = HEADERS_KLASS.new.merge(response[1])
+        @block.call(headers, env)
+        response[1] = headers
+        response
+      end
+    end
+  end
+end