$ git clone -n https://src.fedoraproject.org/rpms/perl-Email-MIME.git /var/lib/mock/f45-build-23291-596/root/chroot_tmpdir/scmroot/perl-Email-MIME
Cloning into '/var/lib/mock/f45-build-23291-596/root/chroot_tmpdir/scmroot/perl-Email-MIME'...
$ git fetch origin 81386f7d658e9cc83565521aba705dfdbac2d34a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Email-MIME
 * [new ref]         81386f7d658e9cc83565521aba705dfdbac2d34a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 81386f7 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild