Disallow ControlPort auto unless ControlPortWriteToFile also set?
If you set controlport auto but you don't set ControlPortWriteToFile, it works, but there's no (automated) way for controllers to find your control port.
A user in #tor just set up his Tor that way.
Should Tor demand that ControlPortWriteToFile is set when ControlPort auto is chosen? Or do we think the use case of "expert user looks at log file and configures controller by hand" outweighs the "user thinks he set it up right but didn't" failure mode?
This is a bug in 0.2.2.x too, but my initial guess is that we don't want to mess with 0.2.2.x here.