$ git clone -n https://src.fedoraproject.org/rpms/rust-coreos-installer.git /var/lib/mock/f40-build-739429-108994/root/chroot_tmpdir/scmroot/rust-coreos-installer
Cloning into '/var/lib/mock/f40-build-739429-108994/root/chroot_tmpdir/scmroot/rust-coreos-installer'...
$ git fetch origin a3ec0a71f952cc9e424d9d7c0a82b8c92fee2e4a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-coreos-installer
 * [new ref]         a3ec0a71f952cc9e424d9d7c0a82b8c92fee2e4a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a3ec0a7 0.18.0