Use Homebrew::EnvConfig.

Library/Homebrew/bottle_publisher.rb

Library/Homebrew/brew.rb

Library/Homebrew/brew.sh

Library/Homebrew/cask/installer.rb

Library/Homebrew/cleanup.rb

Library/Homebrew/cli/parser.rb

Library/Homebrew/cmd/cat.rb

Library/Homebrew/cmd/fetch.rb

Library/Homebrew/cmd/link.rb

Library/Homebrew/cmd/uninstall.rb

Library/Homebrew/cmd/update-report.rb

Library/Homebrew/cmd/update.sh

Library/Homebrew/dev-cmd/bump-formula-pr.rb

Library/Homebrew/dev-cmd/extract.rb

Library/Homebrew/dev-cmd/mirror.rb

Library/Homebrew/dev-cmd/pull.rb

Library/Homebrew/diagnostic.rb

Library/Homebrew/download_strategy.rb

Library/Homebrew/emoji.rb

Library/Homebrew/extend/ARGV.rb