$ git clone -n https://src.fedoraproject.org/rpms/heimdall.git /var/lib/mock/f45-build-13395-450/root/chroot_tmpdir/scmroot/heimdall
Cloning into '/var/lib/mock/f45-build-13395-450/root/chroot_tmpdir/scmroot/heimdall'...
$ git fetch origin c55446bb0fc1d7f0dab91e88d23c46fcefa5bd6a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/heimdall
 * [new ref]         c55446bb0fc1d7f0dab91e88d23c46fcefa5bd6a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c55446b Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild