Allowing PortGroups to bump port revision

[Clemens Lang]

Hi,

On Fri, Jan 12, 2018 at 03:30:50PM -0800, Jeremy Huddleston Sequoia 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'd love to use this feature for updates of GHC. For every new version
of GHC, libraries built with it are installed in a new directory and get
a new ID, which means that I have to find and revbump every haskell port
with such an update.

Unfortunately ports are only re-indexed when their mtime changes, so
while you could just set revision (or epoch, or some other variable) in
a PortGroup, that would still not lead to those ports getting reindexed.

We'd have to keep a map from PortGroup to Portfiles that use this
PortGroup to modify portindex to correctly re-index ports when a
PortGroup changes; note that this might also take quite long. I can
imagine changing the GitHub PortGroup would lead to index update times
of more than 10 minutes. :(

-- 
Clemens