$ git clone -n https://src.fedoraproject.org/rpms/cjkuni-uming-fonts.git /var/lib/mock/f39-build-1591641-38294/root/chroot_tmpdir/scmroot/cjkuni-uming-fonts
Cloning into '/var/lib/mock/f39-build-1591641-38294/root/chroot_tmpdir/scmroot/cjkuni-uming-fonts'...
$ git fetch origin fab13741fe1c76cea3c845278ee451e2ac64031c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/cjkuni-uming-fonts
 * [new ref]         fab13741fe1c76cea3c845278ee451e2ac64031c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fab1374 Fix the spec file