OPT: improve display when choosing the flag -a
OPT: improve display when choosing the flag -a

Former-commit-id: c1e157309f14950ee3d7de90ed691589faf262dc
Former-commit-id: 306892d19df093ea03da74af9c8bebda7a5734c2
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox