Please read pungi prototype wiki page for general overview <https://fedoraproject.org/wiki/Modularity_Working_Group/prototype/pungi>
Just to note that the prototype has split depsolving (pungi-gather binary) and tools for individual deliverables pungi-createrepo, pungi-createiso (which I currently reffer to as pungi-* until we'll have separate docs for each tool)
Check pungi-gather configuration docs <https://pagure.io/fork/lkocman/pungi/blob/modularity-pungi-gather-only/f/doc/pungi-gather-configuration.rst>
pungi-* configuration docs <https://pagure.io/fork/lkocman/pungi/blob/modularity/f/doc/configuration.rst>