Variable: shell-cd-regexp
shell-cd-regexp is a customizable variable defined in shell.el.gz.
Value
"cd"
Documentation
Regexp to match subshell commands equivalent to cd.
Probably introduced at or before Emacs version 17.
Source Code
;; Defined in /usr/src/emacs/lisp/shell.el.gz
(defcustom shell-cd-regexp "cd"
"Regexp to match subshell commands equivalent to cd."
:type 'regexp
:group 'shell-directories)