MongoEngine/mongoengine — pull request #123 by akolechkin (2012-09-09 20:22:13+00:00)
Title: fix broken index inheritance

If you use types inheritance like in changed test case declared indexes are ignored at all.
See the testcase.
in addition, Queryset._build_index_spec is not accurate with python pass-by-value and pass-by-reference behavior, so i added deepcopy this is the only fast fix without breaking everything.