Rivet master update
This is to sync Generators/Rivet_i against the latest version from 21.6.
I took the opportunity to clean up the logic a little (HepMC3 allows to simplify the logic greatly).
Needed for AGENE-1966.
This is to sync Generators/Rivet_i against the latest version from 21.6.
I took the opportunity to clean up the logic a little (HepMC3 allows to simplify the logic greatly).
Needed for AGENE-1966.