$ git clone -n https://src.fedoraproject.org/rpms/os-autoinst.git /var/lib/mock/f40-build-1965602-25205/root/chroot_tmpdir/scmroot/os-autoinst
Cloning into '/var/lib/mock/f40-build-1965602-25205/root/chroot_tmpdir/scmroot/os-autoinst'...
$ git fetch origin a657b2a556c8e1984121f31d88854e64093538a4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/os-autoinst
 * [new ref]         a657b2a556c8e1984121f31d88854e64093538a4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a657b2a Update to latest git