In February 2013, Rubygems 2.0.0 deprecated [1] the `--[no-]ri` and `--[no-]rdoc` options, replacing them with the new `--[no-]document` option.
Almost five years later, Rubygems finally dropped support [2] for the long-deprecated `--[no-]ri` and `--[no-]rdoc` options.
This removal causes `bundle install` to **fail for fresh Homebrew checkouts** if Rubygems 3.0.x or newer is installed, which will happen if the user runs `gem update --system` on Ruby 2.3.0 or later. [3]
This also affects the system Ruby built into macOS 10.13 and 10.14.
Steps to reproduce:
```
$ sudo /usr/bin/gem update -N --system
[…]
Installing RubyGems 3.0.2
ERROR: While executing gem ... (Errno::EPERM)
Operation not permitted @ rb_sysopen - /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/bin/gem
$ gem --version 2>/dev/null
3.0.2
$ cd "$(mktemp -d)"
$ git clone --depth=1 https://github.com/Homebrew/brew.git
[…]
$ cd brew
$ export HOMEBREW_PATH=bin # in case shellcheck is not installed
$ bin/brew style Library/Homebrew/extend/ENV/std.rb
==> Installing or updating 'rubocop' gem
Error: invalid option: --no-ri
```
(Note: The above steps will not touch an existing Homebrew installation, and won’t even require Homebrew to be installed.)
This commit replaces the deprecated options with the new `--no-document` option, which has been around since Rubygems 2.0.0. It is therefore safe for use on all supported platforms.
[1]: https://blog.rubygems.org/2013/02/24/2.0.0-released.html
[2]: https://github.com/rubygems/rubygems/pull/2354
[3]: https://rubygems.org/gems/rubygems-update/versions
This provides a more consistent version for `rubocop` than relying on
`Homebrew.install_gem_setup_path!` (and we really want `brew style` to
provide consistent output).
Adjust the rules based on the current codebase. Remove various enable,
disables and default values that are unnecessary. Add more comments
explaining why. Make minor changes needed to enable a few more rules.
- Don't allow taking an argument. This doesn't work and never has as it
caches the result regardless of the argument.
- Don't rely on the PATH to check for external commands.
`brew cask list` supports the `--full-name` flag which will include the tap
name for casks not part of the core caskroom/cask tap. For example, if
cask "foo-beta" is installed from the caskroom/versions cask, `brew cask
list --full-name` will report the name as "caskroom/versions/foo-beta".
