$ git clone -n https://src.fedoraproject.org/rpms/rubygem-jbuilder.git /var/lib/mock/f40-build-2143361-50854/root/chroot_tmpdir/scmroot/rubygem-jbuilder
Cloning into '/var/lib/mock/f40-build-2143361-50854/root/chroot_tmpdir/scmroot/rubygem-jbuilder'...
$ git fetch origin dd208ec1f756a3f9430d9d729381e3979fa819da:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-jbuilder
 * [new ref]         dd208ec1f756a3f9430d9d729381e3979fa819da -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at dd208ec Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild