REF: improve usage generation of the parser
REF: improve usage generation of the parser

Former-commit-id: a344e87d3c90ab4d02ffe3ecf83497749cbc0797 [formerly 3b873a2e26795f588b6da72779c3169af6c30977]
Former-commit-id: a892b5bc956c8bec0fc87e18f7a56239256cd4a5
Former-commit-id: 22592071523b65617a8aee8a63c232b99b41c756
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox