adds 'cd' command to brew which lets you cd into a formula's directory

brewcd.zsh

unfunction brew &> /dev/null
orig=$(which brew)

function brew() {
    if [[ $1 = 'cd' ]]; then
        dir=$($orig --prefix $2)
        if [[ $? -eq 0 ]]; then
            # cd to the formula's prefix
            cd $dir
        else
            # formula doesn't exist so print brew's error
            $orig --prefix $2
        fi
    else
        # pass on command to brew
        $orig $@
    fi
}