core: Ui#dup works properly

lib/vagrant/ui.rb

@@ -26,6 +26,11 @@ module Vagrant
         @opts     = {}
       end
 
+      def initialize_copy(original)
+        super
+        @opts = original.opts.dup
+      end
+
       [:ask, :detail, :warn, :error, :info, :output, :success].each do |method|
         define_method(method) do |message, *opts|
           # Log normal console messages
@@ -214,6 +219,11 @@ module Vagrant
         @ui     = ui
       end
 
+      def initialize_copy(original)
+        super
+        @ui = original.instance_variable_get(:@ui).dup
+      end
+
       # Use some light meta-programming to create the various methods to
       # output text to the UI. These all delegate the real functionality
       # to `say`.

test/unit/vagrant/ui_test.rb

@@ -237,6 +237,13 @@ describe Vagrant::UI::Prefixed do
 
   subject { described_class.new(ui, prefix) }
 
+  describe "#initialize_copy" do
+    it "duplicates the underlying ui too" do
+      another = subject.dup
+      expect(another.opts).to_not equal(subject.opts)
+    end
+  end
+
   describe "#ask" do
     it "does not request bolding" do
       ui.should_receive(:ask).with("    #{prefix}: foo", bold: false)