Is your feature request related to a problem? Please describe.
IMHO it's a bit awkward to have -f or --feed_name be a required command-line parameter, as it forces you to have a priori knowledge about the dataset you're validating. If given a directory of GTFS zip files with no metadata, it's not a trivial task to find the country code for each.

Describe the solution you'd like
Make -f an optional command-line parameter, where rules that require -f are skipped if -f isn't provided.

IIRC right now the feed name is only used for the country code to validate phone numbers.

@aababilov Thoughts on this? Is this something you could work on?

Describe alternatives you've considered
Clarify how -f parameter should be used in documentation and what happens if you provide a wrong country code, and what the valid values for the name is.