2 files changed, 19 insertions, 14 deletions
diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index 2a1d645859..2ed92ca1ba 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -8,6 +8,8 @@ module ActiveRecord
       alias_method :new, :build
 
       def create!(attrs = nil)
+        ensure_owner_is_not_new
+
         transaction do
           self << (object = attrs ? @reflection.klass.send(:with_scope, :create => attrs) { @reflection.create_association! } : @reflection.create_association!)
           object
@@ -15,6 +17,8 @@ module ActiveRecord
       end
 
       def create(attrs = nil)
+        ensure_owner_is_not_new
+
         transaction do
           self << (object = attrs ? @reflection.klass.send(:with_scope, :create => attrs) { @reflection.create_association } : @reflection.create_association)
           object
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index d5d4808074..09a558a636 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -384,23 +384,11 @@ module ActiveRecord
       end
 
       def rollback(migrations_path, steps=1)
-        migrator = self.new(:down, migrations_path)
-        start_index = migrator.migrations.index(migrator.current_migration)
-
-        return unless start_index
-
-        finish = migrator.migrations[start_index + steps]
-        down(migrations_path, finish ? finish.version : 0)
+        move(:down, migrations_path, steps)
       end
 
       def forward(migrations_path, steps=1)
-        migrator = self.new(:up, migrations_path)
-        start_index = migrator.migrations.index(migrator.current_migration)
-
-        return unless start_index
-
-        finish = migrator.migrations[start_index + steps]
-        up(migrations_path, finish ? finish.version : 0)
+        move(:up, migrations_path, steps)
       end
 
       def up(migrations_path, target_version = nil)
@@ -437,6 +425,19 @@ module ActiveRecord
         # Use the Active Record objects own table_name, or pre/suffix from ActiveRecord::Base if name is a symbol/string
         name.table_name rescue "#{ActiveRecord::Base.table_name_prefix}#{name}#{ActiveRecord::Base.table_name_suffix}"
       end
+
+      private
+
+      def move(direction, migrations_path, steps)
+        migrator = self.new(direction, migrations_path)
+        start_index = migrator.migrations.index(migrator.current_migration)
+
+        if start_index
+          finish = migrator.migrations[start_index + steps]
+          version = finish ? finish.version : 0
+          send(direction, migrations_path, version)
+        end
+      end
     end
 
     def initialize(direction, migrations_path, target_version = nil)