Add logic to Puppet status code

This is used in multiple places now, and it should be boxed up with the
Puppet status anyway.

lib/boxen/puppeteer.rb

@@ -6,6 +6,14 @@ module Boxen
   # Manages an invocation of puppet.
 
   class Puppeteer
+
+    Status = Struct.new(:code) do
+      # Puppet's detailed exit codes reserves 2 for a successful run with changes
+      def success?
+        [0,2].include?(code)
+      end
+    end
+
     attr_reader :config
 
     def initialize(config)
@@ -77,7 +85,7 @@ module Boxen
       warn command.join " " if config.debug?
       Boxen::Util.sudo *command
 
-      $?.exitstatus
+      Status.new($?.exitstatus)
     end
   end
 end

test/boxen_puppeteer_test.rb

@@ -75,4 +75,15 @@ class BoxenPuppeteerTest < Boxen::Test
 
     assert found, "Flags must include #{flag} #{value}."
   end
+
+  def test_status
+    status = Boxen::Puppeteer::Status.new(0)
+    assert status.success?
+
+    status = Boxen::Puppeteer::Status.new(2)
+    assert status.success?
+
+    status = Boxen::Puppeteer::Status.new(1)
+    refute status.success?
+  end
 end