Environment attempts to upgrade box on config load.

If a V1 box is encountered when Vagrant loads the configuration, then it
will be upgraded on the fly.

lib/vagrant/box_collection.rb

@@ -72,13 +72,14 @@ module Vagrant
           raise Errors::BoxUnpackageFailure
         end
 
-        # Verify that the box we just added matches the provider
+        # Get an instance of the box we just added before it is finalized
-        # we expected.
+        # in the system so we can inspect and use its metadata.
         box = Box.new(name, provider, Pathname.new(temp_dir))
 
-        # Verify that the provider matches. If not, then we error and never
+        # Get the provider, since we'll need that to at the least add it
-        # move to the final location.
+        # to the system or check that it matches what is given to us.
         box_provider = box.metadata["provider"]
+
         if provider
           # Verify that the given provider matches what the box has.
           if box_provider.to_sym != provider

lib/vagrant/environment.rb

@@ -426,7 +426,16 @@ module Vagrant
 
         # Second pass, with the box
         box = nil
-        box = boxes.find(config.vm.box, :virtualbox) if config.vm.box
+
+        begin
+          box = boxes.find(config.vm.box, :virtualbox) if config.vm.box
+        rescue Errors::BoxUpgradeRequired
+          # Upgrade the box if we must.
+          @logger.info("Upgrading box during config load: #{config.vm.box}")
+          boxes.upgrade(config.vm.box)
+          retry
+        end
+
         inner_load[subvm, box]
       end
 

test/unit/vagrant/environment_test.rb

@@ -183,6 +183,25 @@ VF
       env.config.for_vm(:bar).ssh.port.should == 200
     end
 
+    it "should load a V1 vagrant box" do
+      environment = isolated_environment do |env|
+        env.vagrantfile(<<-VF)
+Vagrant::Config.run do |config|
+  config.vm.box = "base"
+end
+VF
+
+        env.box("base", <<-VF)
+Vagrant::Config.run do |config|
+  config.ssh.port = 100
+end
+VF
+      end
+
+      env = environment.create_vagrant_env
+      env.config.for_vm(:default).ssh.port.should == 100
+    end
+
     it "should load box configuration" do
       environment = isolated_environment do |env|
         env.vagrantfile(<<-VF)