$ git clone -n https://src.fedoraproject.org/rpms/gtkmm2.4.git /var/lib/mock/f40-build-793445-138983/root/chroot_tmpdir/scmroot/gtkmm2.4
Cloning into '/var/lib/mock/f40-build-793445-138983/root/chroot_tmpdir/scmroot/gtkmm2.4'...
$ git fetch origin 1f96197281f04ce7ab7b4bcfead259a8f1a4f8d1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gtkmm2.4
 * [new ref]         1f96197281f04ce7ab7b4bcfead259a8f1a4f8d1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1f96197 Rebuilt for https://fedoraproject.org/wiki/Fedora_40_Mass_Rebuild