Merge branch 'en/test-selector'

Merge branch 'en/test-selector'

Our test scripts can be told to run only individual pieces while
skipping others with the "--run=..." option; they were taught to
take a substring of test title, in addition to numbers, to name the
test pieces to run.

* en/test-selector:
  test-lib: reduce verbosity of skipped tests
  t6006, t6012: adjust tests to use 'setup' instead of synonyms
  test-lib: allow selecting tests by substring/glob with --run