$ git clone -n https://src.fedoraproject.org/rpms/jopt-simple.git /var/lib/mock/f41-build-818849-14314/root/chroot_tmpdir/scmroot/jopt-simple
Cloning into '/var/lib/mock/f41-build-818849-14314/root/chroot_tmpdir/scmroot/jopt-simple'...
$ git fetch origin af21940befb27b4ad051ca51d9426f079a2c9504:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/jopt-simple
 * [new ref]         af21940befb27b4ad051ca51d9426f079a2c9504 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at af21940 Set Java source/target to 1.8