$ git clone -n https://src.fedoraproject.org/rpms/kf6-knewstuff.git /var/lib/mock/f42-build-side-1-3573578-46768/root/chroot_tmpdir/scmroot/kf6-knewstuff
Cloning into '/var/lib/mock/f42-build-side-1-3573578-46768/root/chroot_tmpdir/scmroot/kf6-knewstuff'...
$ git fetch origin 1a20657734b59a860dae4a6175c570f51cc772fd:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/kf6-knewstuff
 * [new ref]         1a20657734b59a860dae4a6175c570f51cc772fd -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1a20657 6.15 and plasma 3.4 compatibility rebuild