While working on f10691bcc, I noticed this odd comment and decided to
investigate. I wasn't able to reproduce the undesirable behavior because
I cannot get 1.8.7 to compile with rvm but I did notice through some
testing that iTerm2 displays a lock character when echo mode is
disabled. My intent had been to remove this method because Homebrew has
moved past a Ruby version that would necessitate the "hack" but this
method's behavior is actually desirable today, so I changed the comment
to remove the potential flag and instead left a comment explaining
a good second reason for the method.
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.