I've got tags for my code base. I've got tags for my gems. All I'm missing is tags for Ruby stdlib. Until now.
mkdir -p ~/.rbenv/plugins
git clone https://github.com/tpope/rbenv-ctags.git \
~/.rbenv/plugins/rbenv-ctags
rbenv ctags
You'll also need Exuberant Ctags. With Homebrew, brew install ctags.
It is imperative that you make sure the correct ctags binary comes first in
your $PATH. Check ctags --version to verify.
Run rbenv ctags <version> to index the given version. If you are using
ruby-build as an rbenv plugin, this will happen automatically on install.
You need to configure your editor to look for tags files in the Ruby
$LOAD_PATH. If you're using Vim, reasonably recent versions of vim-ruby
(and optionally rbenv.vim) take care of that for you.
You might also want to use rbenv-default-gems to automatically install
gem-ctags. Put it at the top of ~/.rbenv/default-gems so that it
indexes all gems underneath it.