sparse: variable to track if sparse is enabled Currently, the sparse extension sniffs repo instances for attributes defined by the sparse extension to determine if sparse is enabled. As we move code away from repo instances, these checks will be a bit more brittle. We introduce a module-level variable to track whether sparse is enabled as a temporary workaround.

sparse: move profile reading into core One more step towards weaning off methods on repo instances and moving code to core. While this function is only used once and is simple, it needs to exist on its own so Facebook can monkeypatch it to enable simplecache integration.