portupgrade -- is there a way to only build and update ports that actually NEED it?

[John Levine]

>You would think there's an option to portupgrade that says "don't upgrade 
>every single package I've got, but if somewhere in the dependency chain I 
>need a newer version of a thing, then do it."

The problem is that the versioning in the ports system doesn't
distinguish between upgrades that present interface changes and
upgrades that are just nits, new features, or minor bug fixes.
Port makefiles can contain version dependency info, e.g., this
port needs at least version N.M of package X, but few of them do.

This has bitten me in the past with PHP and pcre.  In fact, PHP5
won't work with old versions of pcre, but the PHP port maintainer
refuses to put in version dependency info, because he thinks that
every port should be up to date all the time.

R's,
John