Dont mess with default order engines load

When copying migrations some engines might depend on schema from other
engine so we can't blindly reverse all railties collection as that would
affect the order they were originally loaded. This patch helps to only
apply the order from engines specified in `railties_order`

railties/lib/rails/application.rb

@@ -414,8 +414,14 @@ def y(*objects)
       end
     end
 
+    # Return an array of railties respecting the order they're loaded
+    # and the order specified by the +railties_order+ config.
+    #
+    # While when running initializers we need engines in reverse
+    # order here when copying migrations from railties we need then in the same
+    # order as given by +railties_order+
     def migration_railties # :nodoc:
-      (ordered_railties & railties_without_main_app).reverse
+      ordered_railties.flatten - [self]
     end
 
   protected
@@ -448,11 +454,6 @@ def run_console_blocks(app) #:nodoc:
       super
     end
 
-    def railties_without_main_app # :nodoc:
-      @railties_without_main_app ||= Rails::Railtie.subclasses.map(&:instance) +
-        Rails::Engine.subclasses.map(&:instance)
-    end
-
     # Returns the ordered railties for this application considering railties_order.
     def ordered_railties #:nodoc:
       @ordered_railties ||= begin
@@ -472,13 +473,13 @@ def ordered_railties #:nodoc:
 
         index = order.index(:all)
         order[index] = all
-        order.reverse.flatten
+        order
       end
     end
 
     def railties_initializers(current) #:nodoc:
       initializers = []
-      ordered_railties.each do |r|
+      ordered_railties.reverse.flatten.each do |r|
         if r == self
           initializers += current
         else

railties/test/railties/engine_test.rb

@@ -144,6 +144,42 @@ class CreateBlogs < ActiveRecord::Migration
       end
     end
 
+    test "dont reverse default railties order" do
+      @api = engine "api" do |plugin|
+        plugin.write "lib/api.rb", <<-RUBY
+          module Api
+            class Engine < ::Rails::Engine; end
+          end
+        RUBY
+      end
+
+      # added last but here is loaded before api engine
+      @core = engine "core" do |plugin|
+        plugin.write "lib/core.rb", <<-RUBY
+          module Core
+            class Engine < ::Rails::Engine; end
+          end
+        RUBY
+      end
+
+      @core.write "db/migrate/1_create_users.rb", <<-RUBY
+        class CreateUsers < ActiveRecord::Migration; end
+      RUBY
+
+      @api.write "db/migrate/2_create_keys.rb", <<-RUBY
+        class CreateKeys < ActiveRecord::Migration; end
+      RUBY
+
+      boot_rails
+
+      Dir.chdir(app_path) do
+        output  = `bundle exec rake railties:install:migrations`.split("\n")
+
+        assert_match(/Copied migration \d+_create_users.core_engine.rb from core_engine/, output.first)
+        assert_match(/Copied migration \d+_create_keys.api_engine.rb from api_engine/, output.last)
+      end
+    end
+
     test "mountable engine should copy migrations within engine_path" do
       @plugin.write "lib/bukkits.rb", <<-RUBY
         module Bukkits