We do have a `deprecated` caveat, but we rely on users to bring up that fact, as there's no way the maintainers can keep track of the status of every Cask.
There's also a fairly large push and discussion about removing duplication between Homebrew core and Homebrew Cask, so you should see things improve. There should also be Formula -> renamed Cask migration at some point, the issue has been raised in brew-evolution. (We have basic Cask <-> Formula support already).
Re: terraform specifically, looks like it's now in core, and `brew cask terraform` will know to do `brew install terraform` automatically.
There's also a fairly large push and discussion about removing duplication between Homebrew core and Homebrew Cask, so you should see things improve. There should also be Formula -> renamed Cask migration at some point, the issue has been raised in brew-evolution. (We have basic Cask <-> Formula support already).
Re: terraform specifically, looks like it's now in core, and `brew cask terraform` will know to do `brew install terraform` automatically.