savepoint_name should return nil for non-savepoint transactions

Also add test to assets the savepoint name

activerecord/lib/active_record/connection_adapters/abstract/transaction.rb

@@ -69,6 +69,10 @@ def initialize(connection)
       def state
         @state
       end
+
+      def savepoint_name
+        nil
+      end
     end
 
     class TransactionState
@@ -233,7 +237,8 @@ def initialize(connection, parent, options = {})
 
         super
 
-        @savepoint_name = "active_record_#{number}"
+        # Savepoint name only counts the Savepoint transactions, so we need to subtract 1
+        @savepoint_name = "active_record_#{number - 1}"
         connection.create_savepoint(@savepoint_name)
       end
 

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -358,9 +358,7 @@ def case_insensitive_comparison(table, attribute, column, value)
       end
 
       def current_savepoint_name
-        if current_transaction.is_a? SavepointTransaction
-          current_transaction.savepoint_name
-        end
+        current_transaction.savepoint_name
       end
 
       # Check the connection back in to the connection pool

activerecord/test/cases/transactions_test.rb

@@ -424,6 +424,26 @@ def test_releasing_named_savepoints
     end
   end
 
+  def test_savepoints_name
+    Topic.transaction do
+      assert_nil Topic.connection.current_savepoint_name
+      assert_nil Topic.connection.current_transaction.savepoint_name
+
+      Topic.transaction(requires_new: true) do
+        assert_equal "active_record_1", Topic.connection.current_savepoint_name
+        assert_equal "active_record_1", Topic.connection.current_transaction.savepoint_name
+
+        Topic.transaction(requires_new: true) do
+          assert_equal "active_record_2", Topic.connection.current_savepoint_name
+          assert_equal "active_record_2", Topic.connection.current_transaction.savepoint_name
+        end
+
+        assert_equal "active_record_1", Topic.connection.current_savepoint_name
+        assert_equal "active_record_1", Topic.connection.current_transaction.savepoint_name
+      end
+    end
+  end
+
   def test_rollback_when_commit_raises
     Topic.connection.expects(:begin_db_transaction)
     Topic.connection.expects(:commit_db_transaction).raises('OH NOES')