Check the version before trusting a diagnosis

Situation

A diagnosis from one machine is compared with a repository on another, and nobody knows whether the two ran the same tool.

Scenario

setup: bare
given:
  - 'an empty repository; nothing installed'
steps:
  - id: print
    run: ['version']
    note: 'the one string the projections, the ledger and the site derive their version from'
    expect:
      exit: 0
      stdout_contains: ['^majordomus [0-9]+\.[0-9]+\.[0-9]+$']
  - id: refuse
    run: ['version', '--no-such-option']
    note: 'an argument the command does not know is a usage error, never ignored'
    expect:
      exit: 2
      stdout_contains: ['unknown option --no-such-option']
then:
  - 'the version needs no repository and no installation'
  - 'a usage error exits 2, as the exit-code contract says'

Outcome

version prints the version and nothing else, from anywhere, and refuses an argument it does not understand rather than pretending it did.