Add X11 ssh forwarding option (off by default).

config/default.rb

@@ -12,6 +12,7 @@ Vagrant::Config.run do |config|
   config.ssh.timeout = 30
   config.ssh.private_key_path = File.expand_path("keys/vagrant", Vagrant.source_root)
   config.ssh.forward_agent = false
+  config.ssh.forward_x11 = false
 
   config.vm.auto_port_range = (2200..2250)
   config.vm.box_ovf = "box.ovf"

lib/vagrant/config/ssh.rb

@@ -11,6 +11,7 @@ module Vagrant
       attr_accessor :timeout
       attr_writer :private_key_path
       attr_accessor :forward_agent
+      attr_accessor :forward_x11
 
       def private_key_path
         File.expand_path(@private_key_path, env.root_path)

lib/vagrant/ssh.rb

@@ -42,6 +42,7 @@ module Vagrant
                          "-o StrictHostKeyChecking=no", "-o IdentitiesOnly=yes",
                          "-i #{options[:private_key_path]}"]
       command_options << "-o ForwardAgent=yes" if env.config.ssh.forward_agent
+      command_options << "-o ForwardX11=yes" if env.config.ssh.forward_x11
 
       # Some hackery going on here. On Mac OS X Leopard (10.5), exec fails
       # (GH-51). As a workaround, we fork and wait. On all other platforms,

test/vagrant/ssh_test.rb

@@ -69,6 +69,17 @@ class SshTest < Test::Unit::TestCase
       @ssh.connect
     end
 
+    should "add forward X11 option if enabled" do
+      @env.config.ssh.forward_x11 = true
+      ssh_exec_expect(@ssh.port,
+                      @env.config.ssh.private_key_path,
+                      @env.config.ssh.username,
+                      @env.config.ssh.host) do |args|
+        assert args =~ /-o ForwardX11=yes/
+      end
+      @ssh.connect
+    end
+
     context "on leopard" do
       setup do
         Vagrant::Util::Platform.stubs(:leopard?).returns(true)