ZSH + Apple Terminal: set tab title current working directory for Mojave and earlier

zshrc_Apple_Terminal

# This is a slightly modified version of Mojave (10.14) script located in /etc/bashrc_Apple_Terminal
# modified to work with zsh.
# It mainly calls update_terminal_cwd when changing the working directory, which prints a special
# invisible string that Apple Terminal interprets and updates the current term title accordingly.

# Note : this script is useless for macOS Catalina and newer versions of macOS, since it should
# already contain at least this functionality.

# Instructions
# Place this file in /etc/ (alongside bash_Apple_Terminal)

update_terminal_cwd() {
  # Identify the directory using a "file:" scheme URL, including
  # the host name to disambiguate local vs. remote paths.
  
  # Percent-encode the pathname.
  local url_path=''
  {
    # Use LC_CTYPE=C to process text byte-by-byte. Ensure that
    # LC_ALL isn't set, so it doesn't interfere.
    local i
    local ch
    local hexch
    local LC_CTYPE=C
    local LC_ALL=

    for ((i = 0; i < ${#PWD}; ++i)); do
      ch="${PWD:$i:1}"
      if [[ "$ch" =~ [/._~A-Za-z0-9-] ]]; then
          url_path+="$ch"
      else
          printf -v hexch "%02X" "'$ch"
          # printf treats values greater than 127 as
          # negative and pads with "FF", so truncate.
          url_path+="%${hexch: -2:2}"
      fi
    done
  }

  printf '\e]7;%s\a' "file://$HOSTNAME$url_path"
}

if [ -z "$INSIDE_EMACS" ]; then
    chpwd_functions+=('update_terminal_cwd')
    update_terminal_cwd
fi