Auto install ruby with rbenv

auto-install-ruby-with-rbenv.zsh

# This snippet checks your current directory for a .ruby-version file
# and if it exists, it then checks to see if that version of ruby is
# installed. If not, it will ask you if you want to install it.
#
# Add this snippet to $HOME/.zshrc

# In zsh, the chpwd will run a command every time you change directories.
function chpwd {
  # Check if a .ruby-version file exists
  if [[ -f "$PWD/.ruby-version" ]]; then
    ruby_version=`cat .ruby-version`
    if [[ ! -d "$HOME/.rbenv/versions/$ruby_version" ]]; then
      while true; do
        read REPLY\?"Ruby $ruby_version is not installed. Install it? [Yn] "
        case $REPLY in
          [Yy]* ) rbenv install $ruby_version; break;;
          [Nn]* ) break;;
          * ) echo "Please answer y or n.";;
        esac
      done
    fi
  fi
}