$ git clone -n https://src.fedoraproject.org/rpms/rubygem-multi_xml.git /var/lib/mock/f45-build-35044-693/root/chroot_tmpdir/scmroot/rubygem-multi_xml
Cloning into '/var/lib/mock/f45-build-35044-693/root/chroot_tmpdir/scmroot/rubygem-multi_xml'...
$ git fetch origin 31edb0a55b1c972a868b5c262b645d9588efa47d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-multi_xml
 * [new ref]         31edb0a55b1c972a868b5c262b645d9588efa47d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 31edb0a Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild