rails/rails — pull request #9677 by neerajdotname (2013-03-12 01:08:33+00:00)
Title: SQLite3 3.6.8+ supports nested transactions

http://www.sqlite.org/lang_savepoint.html
https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb#L130-L132