I want to re-use the package.cfg mechanism in rfpkg (for rpmfusion).
I have few others uses cases that are close to the epel8-playground feature.

As a side note, is there plan to move this code into rpkg ? (or should I copy the code I want).

• rpi koji target
  I have few packages that need to be built for the normal koji target along with another koji target. for example: ffmpeg will need to be build with f31-free and f31-rpi (using a separate dist macro).

• multilibs koji target
  With f31 (and el7+) there is another set of packages that need to be built only on a dedicated "multilibs aware" koji target.
  For example: libva-intel-driver will not be built on the default f31-free target but only on f31-free-multilibs

I want to describe the package.cfg configuration for theses packages in a way that will allow me to keep a fast-forward or merge strategy between branches. So having a package.cfg that would be branch agnostic.
And also want to have a mean for this package.cfg computation excluded for some branches (el6 , older fedora).

I'm suggesting to use some magic keyword that would be replaced by the current branch as appropriate, such as:

[koji]
targets = local-branch-free local-branch-rpi
defaults =  el6 f29
or
targets = local-branch-multilibs
defaults = el6 f29 f30

Any better approach ?