- Don't mention options that don't exist in Usage.
- Don't include a log prefix when NO_ARGS is set.
- Turn up the default verbosity to FATAL when NO_ARGS is set.
- Expose verbosity via an ENV var for debugging.
Tini ignores certain signals, and blocks others, but in both cases
we restore them before executing the child process.
Add tests to ensure that we actually do that!
Using the child subreaper mechanism, we can actually run
tests inside the CI environment without depending on Docker.
While this does not replace the existing tests, it allows
at least some functional coverage within CI.