This is one that seems to have been blocking a few projects up until now (going by the number of “any updates?” emails to the forum thread).
The official SPIFFS implementation is now available from the Arduino-ESP32 repository.
That’s the good news. The bad news is that it’s flagged as “initial” and doesn’t seem to have things like “info” support yet. Never mind, we have SPIFFS; thanks Hristo and Ivan!