Bug#681419: Alternative dependencies on non-free packages in main

[Ian Jackson <ijackson@chiark.greenend.org.uk>]

Russ Allbery writes ("Bug#681419: Alternative dependencies on non-free packages in main"):
> Well, if we want to go this route, we could require use of a virtual
> package in all cases like this.  Then foo and foo-nonfree would both
> Provide: foo (and probably Conflicts: foo), and those who want to can
> enable non-free and install foo-nonfree.
> 
> That was one of the options offered in the Policy discussion.

Do we know what proportion of the existing references out of main into
non-free/contrib could be done this way ?

That would at least solve the problem where we put
   Recommends: ... | bar-nonfree ...
in the metadata, which I think is arguably a problem in itself.  It's
difficult to argue that that doesn't constitute a recommendation of
bar-nonfree.

Would we also want to do something to avoid the package managers
complaining about nonexistent virtual packages ?  I guess they are
already happy to ignore references to unprovided virtual packages, and
nonexistent packages in general, since they are a common approach for
transitions and often remain (beneficially) in the dependencies for
years afterwards.

Ian.