$ git clone -n https://src.fedoraproject.org/rpms/unlambda.git /var/lib/mock/f39-build-1507007-35219/root/chroot_tmpdir/scmroot/unlambda
Cloning into '/var/lib/mock/f39-build-1507007-35219/root/chroot_tmpdir/scmroot/unlambda'...
$ git fetch origin fe5ffc6abf2318eb57bff14978fac37546a158b3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/unlambda
 * [new ref]         fe5ffc6abf2318eb57bff14978fac37546a158b3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fe5ffc6 bump release