$ git clone -n https://src.fedoraproject.org/rpms/iperf3.git /var/lib/mock/f40-build-2004799-44994/root/chroot_tmpdir/scmroot/iperf3
Cloning into '/var/lib/mock/f40-build-2004799-44994/root/chroot_tmpdir/scmroot/iperf3'...
$ git fetch origin 7e608c3cd58a06eed28efa7083f11c99f700071b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/iperf3
 * [new ref]         7e608c3cd58a06eed28efa7083f11c99f700071b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7e608c3 update to 3.16