$ git clone -n https://src.fedoraproject.org/rpms/rubygem-jbuilder.git /var/lib/mock/f40-build-2507241-61702/root/chroot_tmpdir/scmroot/rubygem-jbuilder
Cloning into '/var/lib/mock/f40-build-2507241-61702/root/chroot_tmpdir/scmroot/rubygem-jbuilder'...
$ git fetch origin bf5901b8ce33bc32a08293853b1343de1fd0afe3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-jbuilder
 * [new ref]         bf5901b8ce33bc32a08293853b1343de1fd0afe3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bf5901b Rebuilt for https://fedoraproject.org/wiki/Fedora_40_Mass_Rebuild