mxcl/homebrew — comment on commit 3edc9d212b4885568ade6ac79f9cdf34ac3373d5
File: Library/Homebrew/cmd/install.rb line 89
By mislav:

This introduces a bug where `--force` argument is rendered useless. Remember, we only use `--force` on formulae that are already installed. This conditional doesn't repect `--force`.