$ git clone -n https://src.fedoraproject.org/rpms/kf6-purpose.git /var/lib/mock/f42-build-side-1-3585724-46907/root/chroot_tmpdir/scmroot/kf6-purpose
Cloning into '/var/lib/mock/f42-build-side-1-3585724-46907/root/chroot_tmpdir/scmroot/kf6-purpose'...
$ git fetch origin 8690256e1b576b60cebde9429572ba6a35e98cbd:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/kf6-purpose
 * [new ref]         8690256e1b576b60cebde9429572ba6a35e98cbd -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8690256 6.16.0