$ git clone -n https://src.fedoraproject.org/rpms/giac.git /var/lib/mock/f42-build-3356298-45027/root/chroot_tmpdir/scmroot/giac
Cloning into '/var/lib/mock/f42-build-3356298-45027/root/chroot_tmpdir/scmroot/giac'...
$ git fetch origin 8ab8b4628049ad4a408a798990c23d79ac775f96:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/giac
 * [new ref]         8ab8b4628049ad4a408a798990c23d79ac775f96 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8ab8b46 Rebuild with gsl 2.8