$ git clone -n https://src.fedoraproject.org/rpms/flex.git /var/lib/mock/f45-build-9041-398/root/chroot_tmpdir/scmroot/flex
Cloning into '/var/lib/mock/f45-build-9041-398/root/chroot_tmpdir/scmroot/flex'...
$ git fetch origin 6d2702313d2a6eaf942704b16fea874df533bed3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/flex
 * [new ref]         6d2702313d2a6eaf942704b16fea874df533bed3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6d27023 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild