$ git clone -n https://src.fedoraproject.org/rpms/giac.git /var/lib/mock/f40-build-802075-143931/root/chroot_tmpdir/scmroot/giac
Cloning into '/var/lib/mock/f40-build-802075-143931/root/chroot_tmpdir/scmroot/giac'...
$ git fetch origin b6e9a6a683c0be9a6210bf1964e12f4a9d979baa:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/giac
 * [new ref]         b6e9a6a683c0be9a6210bf1964e12f4a9d979baa -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b6e9a6a Undefine GLIBCXX_ASSERTIONS