$ git clone -n https://src.fedoraproject.org/rpms/kf6-purpose.git /var/lib/mock/f42-build-side-1-3499370-45964/root/chroot_tmpdir/scmroot/kf6-purpose
Cloning into '/var/lib/mock/f42-build-side-1-3499370-45964/root/chroot_tmpdir/scmroot/kf6-purpose'...
$ git fetch origin 00c4af0d1bb0fbaa3ad602c0fc88ca2b3b5275e7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/kf6-purpose
 * [new ref]         00c4af0d1bb0fbaa3ad602c0fc88ca2b3b5275e7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 00c4af0 6.13.0