+; TODO commands:
+; - r | read
+; - see timeline ops above
+; - w | write
+; - arg or stdin
+; - nick expand to URI
+; - q | query
+; - see timeline ops above
+; - see hashtag and channels above
+; - d | download
+; - u | upload
+; - calls user-configured command to upload user's own feed file to their server
+; TODO user-agent format: <client>/<version> (+<source.url>; @<source.nick>)
+; - requires configurability
+; - ref: https://twtxt.readthedocs.io/en/latest/user/discoverability.html