Send usage text to stdout if --help specified

[malept]

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.
• The changes are appropriately documented (if applicable).
• The changes have sufficient test coverage (if applicable).
• The testsuite passes successfully on my local machine (if applicable).

Summarize your changes:

--help has never been a defined command line argument, it always just checked for the presence of opts.dir.

Fixes #802.

[codecov]

Codecov Report

Merging #805 into master will decrease coverage by 5%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #805      +/-   ##
==========================================
- Coverage     100%   94.99%   -5.01%     
==========================================
  Files          11       11              
  Lines         579      579              
==========================================
- Hits          579      550      -29     
- Misses          0       29      +29

Impacted Files	Coverage Δ
mac.js	76.27% <0%> (-23.73%)	⬇️
ignore.js	97.36% <0%> (-2.64%)	⬇️

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[malept]

I don't know why codecov thinks there's less code coverage when the file changed isn't covered at all, but 🤷‍♂️ 🚀