Allow nesting temp

lib/configatron/root_store.rb

@@ -20,6 +20,8 @@ class << self
   def initialize
     @locked = false
     @cow = nil
+    @temp_level = 0
+
     reset!
   end
 
@@ -71,17 +73,20 @@ def temp(&block)
   def temp_start
     @temp_locked = @locked
     @temp_cow = @cow
+    @temp_level += 1
 
     # Just need to have a unique Copy-on-Write generation ID
     @cow = @@cow += 1
-    @temp = @store
+    ::Kernel.instance_variable_set("@temp_#{@temp_level}", @store)
   end
 
   def temp_end
     @locked = @temp_locked
     @cow = @temp_cow
 
-    @store = @temp
+    @store = ::Kernel.instance_variable_get("@temp_#{@temp_level}")
+
+    @temp_level -= 1
   end
 
   def locked?

test/functional/configatron.rb

@@ -35,6 +35,17 @@ class Critic::Functional::ConfigatronTest < Critic::Functional::Test
       assert_equal('original', @kernel.foo.bar)
     end
 
+    it 'handles nested temps' do
+      @kernel.temp do
+        @kernel.a = 'Z'
+        @kernel.temp do
+          @kernel.a = 'Y'
+        end
+        assert_equal('Z', @kernel.a)
+      end
+      assert_equal('A', @kernel.a)
+    end
+
     it 'cleans up after an exception' do
       @kernel.foo.bar = 'original'