Allowing PortGroups to bump port revision

[Daniel J. Luke]

On Jan 12, 2018, at 6:30 PM, Jeremy Huddleston Sequoia <jeremyhu at macports.org> wrote:
> In https://trac.macports.org/ticket/54744, we've been pondering adding a PortGroup to allow concurrent installation of multiple providers of the OpenSSL API (eg: openssl, libressl, libressl-devel) and allow ports to specify which they are compatible with.
> 
> It occurred to me that it would be nice if we could update the PortGroup when one of the dependencies changed their dylib id rather than revbumping all ports.  Is this something anyone else has considered?

I've suggested this in the past (for p5 ports, specifically) that we could (ab)use revision to avoid having to rev-bump many ports. (I suggested we use a date-string so that individual ports that used the port-group could still set a higher revision if they needed to - but we'd still probably have to work out something to handle the case where a port wanted to set a revision and then later we wanted to update the revision in the portgroup). 

IIRC Ryan /hated/ that idea.

Alternatively, we could add something to base to let us specify this kind of dependency (which would be useful).

-- 
Daniel J. Luke