$ git clone -n https://src.fedoraproject.org/rpms/diffoscope.git /var/lib/mock/f41-build-815134-149420/root/chroot_tmpdir/scmroot/diffoscope
Cloning into '/var/lib/mock/f41-build-815134-149420/root/chroot_tmpdir/scmroot/diffoscope'...
$ git fetch origin fd67573bae7a7350be0331545f3f62c9d631f903:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/diffoscope
 * [new ref]         fd67573bae7a7350be0331545f3f62c9d631f903 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fd67573 Version 271