Zips every closed day directory (any date before today, UTC) of every feed
under the archive root into <feed_id>/<YYYYMMDD>.zip - exactly the
multi-file input gtfsrealtime::read_gtfsrt_positions() and
read_gtfsrt_trip_updates() ingest - and removes the day directory.
Arguments
- dir
Archive root directory (as used by
rt2s_collect).