Another attempt at fixing `brew audit` issues around detecting
`revision` and `version_scheme` changes correctly. First done in #1754
and #2086 (reverted in #2099 and #2100).
To ease future debugging a `ph` helper has been added to print a hash
and a series of RSpec tests to verify that the `revision`,
`version_scheme` and `version` formula version audits behave as
expected.
Fixes#1731.
This is the (partially) documented public API for Homebrew.
The main class you should look at is the {Formula} class (and classes linked from there). That's the class that's used to create Homebrew formulae (i.e. package descriptions). Assume anything else you stumble upon is private.