Implement command completion in remote shells. (Bug#31704)

* doc/lispref/files.texi (Locating Files): Describe optional
argument REMOTE of `executable-find'.
(Magic File Names): Add `exec-path'.

* doc/lispref/processes.texi (Subprocess Creation): Describe
function `exec-path'.

* doc/misc/tramp.texi (Remote programs): Explain refresh of search
paths by `tramp-cleanup-this-connection'.

* etc/NEWS: Mention 'exec-path' and 'executable-find'.

* lisp/files.el (exec-path): New defun.
(executable-find): Add optional argument REMOTE.

* lisp/shell.el (shell-completion-vars): Set `comint-file-name-prefix'.
(shell--command-completion-data): Use `(exec-path)'.  (Bug#31704)

* lisp/net/ange-ftp.el (exec-path):
* lisp/net/tramp.el (tramp-file-name-for-operation):
* lisp/net/tramp-adb.el (tramp-adb-file-name-handler-alist):
* lisp/net/tramp-archive.el (tramp-archive-file-name-handler-alist):
* lisp/net/tramp-gvfs.el (tramp-gvfs-file-name-handler-alist):
* lisp/net/tramp-sh.el (tramp-sh-file-name-handler-alist):
* lisp/net/tramp-smb.el (tramp-smb-file-name-handler-alist)
<exec-path>: Add handler.

* lisp/net/tramp-adb.el (tramp-adb-handle-exec-path): New defun.
(tramp-adb-maybe-open-connection): Do not set "remote-path"
connection property.

* lisp/net/tramp-compat.el (tramp-compat-exec-path): New defun.

* lisp/net/tramp-sh.el (tramp-sh-handle-exec-path): New defun.

* lisp/net/tramp.el (tramp-eshell-directory-change): Use it.

* test/lisp/net/tramp-archive-tests.el
(tramp-archive-test38-make-nearby-temp-file)
(tramp-archive-test41-file-system-info)
(tramp-archive-test43-auto-load)
(tramp-archive-test43-delay-load): Rename.

* test/lisp/net/tramp-tests.el (tramp-test34-exec-path): New test.
(tramp-test36-make-auto-save-file-name)
(tramp-test37-find-backup-file-name)
(tramp-test38-make-nearby-temp-file)
(tramp-test39-special-characters)
(tramp-test39-special-characters-with-stat)
(tramp-test39-special-characters-with-perl)
(tramp-test39-special-characters-with-ls, tramp-test40-utf8)
(tramp-test40-utf8-with-stat, tramp-test40-utf8-with-perl)
(tramp-test40-utf8-with-ls, tramp-test41-file-system-info)
(tramp-test42-asynchronous-requests, tramp-test43-auto-load)
(tramp-test43-delay-load, tramp-test43-recursive-load)
(tramp-test43-remote-load-path, tramp-test44-unload): Rename.

1 files changed, 8 insertions, 3 deletions

diff --git a/lisp/shell.el b/lisp/shell.el
index 232186083d5..91c65ed171e 100644
--- a/lisp/shell.el
+++ b/lisp/shell.el
@@ -468,6 +468,8 @@ Shell buffers.  It implements `shell-completion-execonly' for
   (set (make-local-variable 'comint-file-name-chars) shell-file-name-chars)
   (set (make-local-variable 'comint-file-name-quote-list)
        shell-file-name-quote-list)
+  (set (make-local-variable 'comint-file-name-prefix)
+       (file-remote-p default-directory))
   (set (make-local-variable 'comint-dynamic-complete-functions)
        shell-dynamic-complete-functions)
   (setq-local comint-unquote-function #'shell--unquote-argument)
@@ -1170,9 +1172,12 @@ Returns t if successful."
          (start (if (zerop (length filename)) (point) (match-beginning 0)))
          (end (if (zerop (length filename)) (point) (match-end 0)))
 	 (filenondir (file-name-nondirectory filename))
-	 ; why cdr? see `shell-dynamic-complete-command'
-	 (path-dirs (append (cdr (reverse exec-path))
-	   (if (memq system-type '(windows-nt ms-dos)) '("."))))
+	 (path-dirs
+	  ;; Ignore `exec-directory', the last entry in `exec-path'.
+          (append (cdr (reverse (exec-path)))
+	          (if (and (memq system-type '(windows-nt ms-dos))
+                           (not (file-remote-p default-directory)))
+                      '("."))))
 	 (cwd (file-name-as-directory (expand-file-name default-directory)))
 	 (ignored-extensions
 	  (and comint-completion-fignore