Merge remote branch 'rails/master' into identity_map

Conflicts:
	activerecord/examples/performance.rb
	activerecord/lib/active_record/association_preload.rb
	activerecord/lib/active_record/associations.rb
	activerecord/lib/active_record/associations/association_proxy.rb
	activerecord/lib/active_record/autosave_association.rb
	activerecord/lib/active_record/base.rb
	activerecord/lib/active_record/nested_attributes.rb
	activerecord/test/cases/relations_test.rb

1 files changed, 18 insertions, 4 deletions

diff --git a/actionpack/lib/action_view/helpers/asset_tag_helpers/asset_include_tag.rb b/actionpack/lib/action_view/helpers/asset_tag_helpers/asset_include_tag.rb
index e52797042f..52eb43a1cd 100644
--- a/actionpack/lib/action_view/helpers/asset_tag_helpers/asset_include_tag.rb
+++ b/actionpack/lib/action_view/helpers/asset_tag_helpers/asset_include_tag.rb
@@ -11,7 +11,9 @@ module ActionView
         attr_reader :config, :asset_paths
 
         class_attribute :expansions
-        self.expansions = { }
+        def self.inherited(base)
+          base.expansions = { }
+        end
 
         def initialize(config, asset_paths)
           @config = config
@@ -69,9 +71,21 @@ module ActionView
             if sources.first == :all
               collect_asset_files(custom_dir, ('**' if recursive), "*.#{extension}")
             else
-              sources.collect do |source|
-                determine_source(source, expansions)
-              end.flatten
+              sources.inject([]) do |list, source|
+                determined_source = determine_source(source, expansions)
+                update_source_list(list, determined_source)
+              end
+            end
+          end
+
+          def update_source_list(list, source)
+            case source
+            when String
+              list.delete(source)
+              list << source
+            when Array
+              updated_sources = source - list
+              list.concat(updated_sources)
             end
           end