how to keep PORTVERSION from going backwards?

[Mike Brown]

How should I handle this?

The software vendor version numbers go like this:
1.0b3 (older release)
1.0 (current release)
1.0.1 (upcoming release)

The port currently has PORTVERSION = 1.0.b3, and has not made use of 
DISTVERSION.

What's a good way to set PORTVERSION (and DISTVERSION, if needed) when I
update the port to the current and upcoming releases? I don't want the
PORTVERSION to go backwards. I assume that's what would happen if I set
it to just match the vendor's version numbers, and I assume that's bad.

Thanks for any advice!
Mike