Filter out unwanted angencies to speed up feed update time?

[elad661]

I have a GTFS files with a bunch of different agencies, but I'm only interested in the data for one of them.
it'd be very useful for me if there was a mechanism to skip insertion of routes that don't belong to that specific agencies, and after all the routes I want are in and the rest are out, skip insertion of Trips, StopTimes and Shapes that belongs to routes which are not in the DB.