$ git clone -n https://src.fedoraproject.org/rpms/cmatrix.git /var/lib/mock/f40-build-789754-135974/root/chroot_tmpdir/scmroot/cmatrix
Cloning into '/var/lib/mock/f40-build-789754-135974/root/chroot_tmpdir/scmroot/cmatrix'...
$ git fetch origin 70b973b6cb7a8a004bf9499294f0e4df7b378d21:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/cmatrix
 * [new ref]         70b973b6cb7a8a004bf9499294f0e4df7b378d21 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 70b973b Rebuilt for https://fedoraproject.org/wiki/Fedora_40_Mass_Rebuild