A custom brew formulae which will not conflict with existing helm 3 installations. Useful for migrating versions while maintaining compatibility.
You may also want to pin existing helm 2 installations incase the official formulae is updated to helm 3.
brew pin kubernetes-helm
brew install vaionicle/kubernetes-helm-2/kubernetes-helm-2
Or
brew tap vaionicle/kubernetes-helm-2
brew install kubernetes-helm-2
helm version
brew help
, man brew
or check Homebrew's documentation.