To enable https://github.com/flutter/flutter/issues/83706

Formatting is loosely based on what `Brew` does, and open to suggestions.  Existing tests are unchanged.

Example (all displayed commands categorized):
<img width="669" alt="Screenshot 2021-07-23 at 16 22 40" src="https://user-images.githubusercontent.com/6655696/126796093-e8652385-c3d7-4600-83b1-76852ab46ea4.png">