$ git clone -n https://src.fedoraproject.org/rpms/rust-ar.git /var/lib/mock/f42-build-58868857-6568656/root/chroot_tmpdir/scmroot/rust-ar
Cloning into '/var/lib/mock/f42-build-58868857-6568656/root/chroot_tmpdir/scmroot/rust-ar'...
$ git fetch origin 493499e827ee016f9197b3526c84f3136afa78e0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-ar
 * [new ref]         493499e827ee016f9197b3526c84f3136afa78e0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 493499e Revive rust-ar with version 0.9.0