$ git clone -n https://src.fedoraproject.org/rpms/HepMC3.git /var/lib/mock/f39-build-1641270-40181/root/chroot_tmpdir/scmroot/HepMC3
Cloning into '/var/lib/mock/f39-build-1641270-40181/root/chroot_tmpdir/scmroot/HepMC3'...
$ git fetch origin c1774baab70299628f1e67cb05f8fb714f8f83a5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/HepMC3
 * [new ref]         c1774baab70299628f1e67cb05f8fb714f8f83a5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c1774ba Update to version 3.2.7