$ git clone -n https://src.fedoraproject.org/rpms/kf5-knewstuff.git /var/lib/mock/f38-build-729635-101821/root/chroot_tmpdir/scmroot/kf5-knewstuff
Cloning into '/var/lib/mock/f38-build-729635-101821/root/chroot_tmpdir/scmroot/kf5-knewstuff'...
$ git fetch origin aa83be81ddb0e0413444a03911988de4fb3e6973:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/kf5-knewstuff
 * [new ref]         aa83be81ddb0e0413444a03911988de4fb3e6973 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at aa83be8 5.107.0