Fix Bug#31704

* lisp/eshell/esh-proc.el (eshell-gather-process-output): Do not
let `expand-file-name' prefix remote file names with MS Windows
volume letter.

* lisp/net/tramp.el (tramp-eshell-directory-change):
Use `path-separator' as it does eshell.  (Bug#31704)

lisp/eshell/esh-proc.el

@@ -282,11 +282,10 @@ See `eshell-needs-pipe'."
 	    (let ((process-connection-type
 		   (unless (eshell-needs-pipe-p command)
 		     process-connection-type))
-		  (command (file-local-name command)))
-	      (apply 'start-file-process
-		     (file-name-nondirectory command) nil
 		  ;; `start-process' can't deal with relative filenames.
-		     (append (list (expand-file-name command)) args))))
+		  (command (file-local-name (expand-file-name command))))
+	      (apply 'start-file-process
+		     (file-name-nondirectory command) nil command args)))
       (eshell-record-process-object proc)
       (set-process-buffer proc (current-buffer))
       (if (eshell-interactive-output-p)

lisp/net/tramp.el

@@ -4623,8 +4623,10 @@ Only works for Bourne-like shells."
 (defun tramp-eshell-directory-change ()
   "Set `eshell-path-env' to $PATH of the host related to `default-directory'."
   ;; Remove last element of `(exec-path)', which is `exec-directory'.
+  ;; Use `path-separator' as it does eshell.
   (setq eshell-path-env
-	(mapconcat 'identity (butlast (tramp-compat-exec-path)) ":")))
+	(mapconcat
+	 'identity (butlast (tramp-compat-exec-path)) path-separator)))
 
 (eval-after-load "esh-util"
   '(progn