Ability to specify no parallelism on the environment

lib/vagrant/environment.rb

@@ -197,9 +197,11 @@ module Vagrant
     #
     # This handles the case where batch actions are disabled by the
     # VAGRANT_NO_PARALLEL environmental variable.
-    def batch
+    def batch(disable_parallel=false)
+      disable_parallel ||= !!ENV["VAGRANT_NO_PARALLEL"]
+
       @batch_lock.synchronize do
-        BatchAction.new(!!ENV["VAGRANT_NO_PARALLEL"]).tap do |b|
+        BatchAction.new(disable_parallel).tap do |b|
           # Yield it so that the caller can setup actions
           yield b
 

test/unit/vagrant/environment_test.rb

@@ -64,6 +64,15 @@ describe Vagrant::Environment do
           instance.batch {}
         end
       end
+
+      it "should run with disabling parallelization if explicit" do
+        with_temp_env("VAGRANT_NO_PARALLEL" => nil) do
+          Vagrant::BatchAction.should_receive(:new).with(true).and_return(batch)
+          batch.should_receive(:run)
+
+          instance.batch(true) {}
+        end
+      end
     end
 
     context "with the disabling env var" do