This plugin’s behavior has been made standard in ruby-build,
rendering it obsolete.

Automatically link rbenv Ruby installs to readline on OS X

OS X ships with editline rather than readline, and by default any Ruby
you compile on it will use the former rather than the latter. This rbenv
plugin’s sole purpose is to tell ruby-build to link to a Homebrew
installed readline instead.

The particular problem this was created to solve was getting the ironically
named pry-editline to consistently work across my Ruby installs. This is
by no means the only reason to eschew editline.

Installation

git clone git://github.com/tpope/rbenv-readline.git \
  ~/.rbenv/plugins/rbenv-readline