$ git clone -n https://src.fedoraproject.org/rpms/iperf3.git /var/lib/mock/eln-build-side-115021-61036634-6588089/root/chroot_tmpdir/scmroot/iperf3
Cloning into '/var/lib/mock/eln-build-side-115021-61036634-6588089/root/chroot_tmpdir/scmroot/iperf3'...
$ git fetch origin fb5a7177aa5317662c7548ee70973d1ca16fb5c9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/iperf3
 * [new ref]         fb5a7177aa5317662c7548ee70973d1ca16fb5c9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fb5a717 Update to 3.19. Fixes rhbz#2366951