port_binary_distributable.tcl: Clarify reason for nondistributability

[ryandesign (Ryan Carsten Schmidt)]

Could port_binary_distributable.tcl in verbose mode provide more details on why a port is not distributable? Many developers, myself included, struggle to understand what if anything can be done to resolve nondistributability when the only information the script provides is e.g.:

"emacs-app" is not distributable because its license "gpl" conflicts with license "OpenSSL" of dependency "openssl"

It is not easy for a developer to figure out the chain of dependencies that leads to the dependency with the conflicting license. port rdeps doesn't help because it only lists each dependency once, even if that one occurrence is in a dependency chain that is not participating in distributability checks due to installs_libs no, and port rdeps --full produces too much output to be usable.

The problem is made more difficult when a port has different dependencies on different OS versions (e.g. due to needing a newer compiler or cctools or git on older systems), resulting in different distributability on different OS versions (#54633, #59926). Maintainers usually doesn't have direct access to multiple OS version to investigate.

I have often wanted to have a MacPorts command to show the chain(s) of dependencies relating one port to another. Maybe if that existed, port_binary_distributable.tcl could use it.

[mascguy (Christopher Nielsen)]

Open PR related to this:

​PR 14 - port_binary_distributable: more verbose description of failures

[mascguy (Christopher Nielsen)]

@Danchr, are you interested in completing this work? If not I'll run with it, as it looks like you're very close. We just need to make the changes requested by folks.