port upgrade outdated order

[Lawrence Velázquez]

On Mar 4, 2015, at 1:59 PM, René J.V. Bertin <rjvbertin at gmail.com> wrote:

> @ larry
>> Base doesn't have a concept of equivalence. It doesn't know that qt5-mac and
>> qt5-mac-devel are interchangeable. We could implement virtual ports or
>> something like that, but that's a rather larger project.
> 
> Would be more like Debian's "replaces", no?

I'm not very familiar with dpkg/apt or how it handles this problem.

> @ Clemens
>> There's an easy explanation: Let's assume
>> while qt5 and qt5-devel provide different versions of the same software,
>> they're still not binary-compatible.
> 
> Actually, Qt makes it a point to be binary compatible between point releases, but you have a point.
> However, my initial argument concerned subports of one and the same main port, there ought not be ABI issues there.

Subports are not special. They are just organizational tools for portfile code; they have no semantic significance. For instance:

- The `file` port has a subport `libmagic` that installs a library.
- The `curl` port has a subport `curl-ca-bundle` that installs certificates.
- The `php` port has many, many subports that install the PHP interpreters and extensions.

The point is that one cannot assume *anything* about a port, its subports, and their relationship.

vq