core: MachineIndex stores the box associated with a machine when ID is set

lib/vagrant/machine.rb

@@ -254,6 +254,7 @@ module Vagrant
         if index_uuid.nil?
           # Create the index entry and save it
           entry = MachineIndex::Entry.new
+          entry.extra_data["box"] = @config.vm.box
           entry.local_data_path = @env.local_data_path
           entry.name = @name.to_s
           entry.provider = @provider_name.to_s

lib/vagrant/machine_index.rb

@@ -378,6 +378,8 @@ module Vagrant
       # The parameter given should be nil if this is being created
       # publicly.
       def initialize(id=nil, raw=nil)
+        @extra_data = {}
+
         # Do nothing if we aren't given a raw value. Otherwise, parse it.
         return if !raw
 

test/unit/vagrant/machine_test.rb

@@ -403,11 +403,22 @@ describe Vagrant::Machine do
     end
 
     it "is set one when setting an ID" do
+      subject.config.vm.box = "FOO"
       subject.id = "foo"
 
       uuid = subject.index_uuid
       expect(uuid).to_not be_nil
       expect(new_instance.index_uuid).to eq(uuid)
+
+      # Test the entry itself
+      entry = env.machine_index.get(uuid)
+      expect(entry.extra_data["box"]).to eq(subject.config.vm.box)
+      expect(entry.name).to eq(subject.name)
+      expect(entry.provider).to eq(subject.provider_name.to_s)
+      expect(entry.state).to eq("preparing")
+      expect(entry.vagrantfile_path).to eq(env.root_path)
+      expect(entry.vagrantfile_name).to eq(env.vagrantfile_name)
+      env.machine_index.release(entry)
     end
 
     it "deletes the UUID when setting to nil" do