040000 tree 228bb9bd73eb28f41e21b93500b892e8e04a3efb	gflags
040000 tree 1bbfe6a93badfcec0c296351e04bc7596e2596e0	msgpack-cxx
040000 tree 3e65b230f8d0bb5b27ad0c37f5796147d5854f40	robin-hood-hashing