$ git clone -n https://src.fedoraproject.org/rpms/icestorm.git /var/lib/mock/f42-build-side-1-3523426-46206/root/chroot_tmpdir/scmroot/icestorm
Cloning into '/var/lib/mock/f42-build-side-1-3523426-46206/root/chroot_tmpdir/scmroot/icestorm'...
$ git fetch origin cba1ac5e55c28ee1a6bf8fb10aeae7574cab2f5e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/icestorm
 * [new ref]         cba1ac5e55c28ee1a6bf8fb10aeae7574cab2f5e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cba1ac5 update to newer snapshot