$ git clone -n https://src.fedoraproject.org/rpms/rust-num-bigint0.3.git /var/lib/mock/f42-build-side-1-3500301-45970/root/chroot_tmpdir/scmroot/rust-num-bigint0.3
Cloning into '/var/lib/mock/f42-build-side-1-3500301-45970/root/chroot_tmpdir/scmroot/rust-num-bigint0.3'...
$ git fetch origin 8292173807b3ae38635a34749d5a00a20f8070f4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-num-bigint0.3
 * [new ref]         8292173807b3ae38635a34749d5a00a20f8070f4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8292173 Drop unused optional support for arbitrary v0.4