You have to hold your course. You are supposed to pass port to port. He should not turn to port but to stb if anything. You should not tack as you would be turning in the direction he should if required to give you more room.
Guess I'm really in the minority here, but David was burdened and acknowledged as much in his post.
So, it's not for him to hold his course - it's his obligation to alter course if it appears there's not enough room to pass/cross safely.
Passing port-to-port may be conventional, but I'd never take it that "You are supposed to pass port to port.".
The other boat should not have to alter course at all - it was David's responsibility.
In the original post, David says there was room to pass with both boats maintaining their respective courses. In my opinion, that's what should have happened.
And, yes, a sound signal or radio call would have reduced whatever pucker factor may have been in the offing.
PS Yes, he was a nice guy!!!