Quiet initial "learned some more directory information" log message
On initial bootstrap, we get
Sep 03 19:15:34.000 [notice] Reloaded microdescriptor cache. Found 0 descriptors. Sep 03 19:15:34.000 [notice] I learned some more directory information, but not enough to build a circuit: We have no usable consensus. Sep 03 19:15:35.000 [notice] Bootstrapped 5%: Connecting to directory server. Sep 03 19:15:35.000 [notice] Heartbeat: Tor's uptime is 0:00 hours, with 1 circuits open. I've sent 0 kB and received 0 kB.
The "bootstrapped 5%" line is useful (more precisely, its absence is useful).
The "learned some more directory information" line is actually false in this case though: it got triggered because we called directory_info_has_arrived() from do_main_loop(), to jumpstart it into calling update_all_descriptor_downloads() for us.
The only case where we call directory-info-has-arrived with from_cache == 1 is this initial jumpstarting case.
I suggest we quiet the log message when from_cache is 1.