this is to enhance the tarsum algorithm, but _MUST_ be done in lock step
with the same for docker-registry. (PR will be cited)
Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
Upstream-commit: 448c8ecb0fb453bb29fcada5e7486355ccfadbe9
Component: engine