Fixed tests and include tag code to use register's file_system

lib/liquid/tags/include.rb

@@ -73,7 +73,7 @@ module Liquid
         if cached = cached_partials[template_name]
           cached
         else
-          if @partial && context.registers[:file_system].nil?
+          if @partial
             partial = @partial
           else
             partial = Liquid::Template.parse(read_template_from_file_system(context), pass_options)
@@ -85,7 +85,7 @@ module Liquid
       end
 
       def read_template_from_file_system(context)
-        file_system = context.registers[:file_system] || parsed_file_system || Liquid::Template.file_system
+        file_system = context.registers[:file_system] || Liquid::Template.file_system
 
         file_system.read_template_file(context[@template_name])
       end

test/integration/tags/include_tag_test.rb

@@ -86,17 +86,12 @@ class IncludeTagTest < Minitest::Test
 
   def test_include_tag_can_use_file_system_at_parse_so_it_can_be_parsed_before_rendered
     assert_equal 'from ParseFileSystem',
-      Template.parse("{% include 'pick_a_source' %}",file_system: ParseFileSystem.new).render!({})
-  end
-
-  def test_include_tag_looks_at_file_system_passed_in_registers_over_parse_options
-    assert_equal 'from OtherFileSystem',
       Template.parse("{% include 'pick_a_source' %}",file_system: ParseFileSystem.new).render!({}, :registers => {:file_system => OtherFileSystem.new})
   end
 
-  def test_include_tag_use_parse_option_file_system_even_if_partial_can_be_preparsed
-    assert_equal 'from ParseFileSystem',
-      Template.parse("{% include template %}",file_system: ParseFileSystem.new).render!({})
+  def test_include_tag_use_registers_file_system_when_it_cant_be_preparse
+    assert_equal 'from OtherFileSystem',
+      Template.parse("{% include template %}",file_system: ParseFileSystem.new).render!({}, :registers => {:file_system => OtherFileSystem.new})
   end 
 
   def test_include_tag_with