Toggle directory tracking in shell buffers (Dirtrack mode).
With a prefix argument ARG, enable Dirtrack mode if ARG is
positive, and disable it otherwise. If called from Lisp, enable
the mode if ARG is omitted or nil.
This method requires that your shell prompt contain the current
working directory at all times, and that you set the variable
`dirtrack-list' to match the prompt.
This is an alternative to `shell-dirtrack-mode', which works by
tracking `cd' and similar commands which change the shell working directory. (fn &optional ARG)