[gentoo-user] Blacklisting all packages from overlay except a specific group and version

[Nikos Chantziaras]

So, I want to install packages from an overlay, but only from a specific 
group. In this case, the dev-qt/ group. The overlay name is "qt".

It doesn't work:
  package.mask: */*::qt
  package.unmask: dev-qt/*-5.6*::qt

With this, 5.6 versions are still masked.

How do I do this?