Re: Small shell-mode patch to handle auto-cd (e.g. shells like zsh)

[Jason Kim <jason.w.kim@icloud.com>]

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Hi, enclosed is what I hope is an acceptable git-format-patch for this 
tiny change.

If not, please let me know how to fix!

Thanks!
-Jason




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From 7dca68a6289abb1800b2dccfd26efe0e85aad6a4 Mon Sep 17 00:00:00 2001
From: Jason Kim <jason.kim@revtera.com>
Date: Fri, 7 May 2021 09:41:11 -0700
Subject: [PATCH] Add a defcustom to shell-mode to handle auto-cd feature (e.g.
 zsh)

shell-has-auto-cd is a new defcustom (default: nil) for
users with shells like zsh that can auto-cd into a directory
without typing in the "cd" command.
If set to true and the command is a directory, then shell-mode
processes the command (which happens to be a directory) as if it
were prepended with "cd"
---
 lisp/shell.el | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/lisp/shell.el b/lisp/shell.el
index 3098d3a14d..8b3499ccb4 100644
--- a/lisp/shell.el
+++ b/lisp/shell.el
@@ -321,6 +321,13 @@ Thus, this does not include the shell's current directory.")
 (defvar shell-dirstack-query nil
   "Command used by `shell-resync-dirs' to query the shell.")
 
+(defcustom shell-has-auto-cd nil
+  "If non-nil, `shell-mode' will automatically process implicit \"cd\" commands.
+Implicit \"cd\" is changing the directory if the command happens to be a directory.
+You can make this variable buffer-local to change it, per shell-mode instance
+Useful for shells like zsh that has this feature.")
+
+
 (defvar shell-mode-map
   (let ((map (make-sparse-keymap)))
     (define-key map "\C-c\C-f" 'shell-forward-command)
@@ -836,13 +843,15 @@ Environment variables are expanded, see function `substitute-in-file-name'."
 			       str) ; skip whitespace
 			      (match-end 0)))
 		(case-fold-search)
-		end cmd arg1)
+		end cmd arg1 cmd-subst-fn)
 	    (while (string-match shell-command-regexp str start)
 	      (setq end (match-end 0)
 		    cmd (comint-arguments (substring str start end) 0 0)
 		    arg1 (comint-arguments (substring str start end) 1 1))
 	      (if arg1
 		  (setq arg1 (shell-unquote-argument arg1)))
+              (if shell-has-auto-cd
+                  (setq cmd-subst-fn (comint-substitute-in-file-name cmd)))
 	      (cond ((string-match (concat "\\`\\(" shell-popd-regexp
 					   "\\)\\($\\|[ \t]\\)")
 				   cmd)
@@ -859,7 +868,9 @@ Environment variables are expanded, see function `substitute-in-file-name'."
 			  (string-match (concat "\\`\\(" shell-chdrive-regexp
 						"\\)\\($\\|[ \t]\\)")
 					cmd))
-		     (shell-process-cd (comint-substitute-in-file-name cmd))))
+		     (shell-process-cd (comint-substitute-in-file-name cmd)))
+                    ((and shell-has-auto-cd (file-directory-p cmd-subst-fn))
+                     (shell-process-cd cmd-subst-fn)))
 	      (setq start (progn (string-match shell-command-separator-regexp
 					       str end)
 				 ;; skip again
-- 
2.25.1