$ git clone -n https://src.fedoraproject.org/rpms/rubygem-jbuilder.git /var/lib/mock/f45-build-35041-693/root/chroot_tmpdir/scmroot/rubygem-jbuilder
Cloning into '/var/lib/mock/f45-build-35041-693/root/chroot_tmpdir/scmroot/rubygem-jbuilder'...
$ git fetch origin e54371db77fa02711dd0eed3f099f33bc9cbd3e5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-jbuilder
 * [new ref]         e54371db77fa02711dd0eed3f099f33bc9cbd3e5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e54371d Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild