$ git clone -n https://src.fedoraproject.org/rpms/Rex.git /var/lib/mock/f39-build-1628750-39484/root/chroot_tmpdir/scmroot/Rex
Cloning into '/var/lib/mock/f39-build-1628750-39484/root/chroot_tmpdir/scmroot/Rex'...
$ git fetch origin 2bf35965bbc3003787bcc1f5cd68563b81cf4dab:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/Rex
 * [new ref]         2bf35965bbc3003787bcc1f5cd68563b81cf4dab -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2bf3596 Update to 1.14.3 (#2229419)