Unify "."" and ".." handling in tramp-*-file-name-all-completions

* lisp/net/tramp-adb.el (tramp-adb-handle-file-name-all-completions):
* lisp/net/tramp-fuse.el (tramp-fuse-handle-file-name-all-completions):
* lisp/net/tramp-gvfs.el (tramp-gvfs-handle-file-name-all-completions):
Remove special handling of "." an "..".

* lisp/net/tramp.el (tramp-skeleton-file-name-all-completions):
Handle ".""  and "..".

lisp/net/tramp-adb.el

@@ -450,14 +450,10 @@ Emacs dired can't find files."
 		(file-name-as-directory f)
 	      f))
 	  (with-current-buffer (tramp-get-buffer v)
-	    (append
-	     ;; On some file systems like "sdcard", "." and ".." are
-	     ;; not included.
-	     '("." "..")
-	     (mapcar
-	      (lambda (l)
-		(and (not (string-match-p (rx bol (* blank) eol) l)) l))
-	      (split-string (buffer-string) "\n" 'omit))))))))))
+	    (mapcar
+	     (lambda (l)
+	       (and (not (string-match-p (rx bol (* blank) eol) l)) l))
+	     (split-string (buffer-string) "\n" 'omit)))))))))
 
 (defun tramp-adb-handle-file-local-copy (filename)
   "Like `file-local-copy' for Tramp files."

lisp/net/tramp-fuse.el

@@ -106,17 +106,8 @@
     (tramp-fuse-remove-hidden-files
      (all-completions
       filename
-      (append
-       (file-name-all-completions
-	filename (tramp-fuse-local-file-name directory))
-       ;; Some storage systems do not return "." and "..".
-       (let (result)
-	 (dolist (item '(".." ".") result)
-	   (when (string-prefix-p filename item)
-	     (catch 'match
-	       (dolist (elt completion-regexp-list)
-		 (unless (string-match-p elt item) (throw 'match nil)))
-	       (setq result (cons (concat item "/") result)))))))))))
+      (file-name-all-completions
+       filename (tramp-fuse-local-file-name directory))))))
 
 ;; This function isn't used.
 (defun tramp-fuse-handle-insert-directory

lisp/net/tramp-gvfs.el

@@ -1469,7 +1469,7 @@ If FILE-SYSTEM is non-nil, return file system attributes."
        filename
        (with-parsed-tramp-file-name (expand-file-name directory) nil
 	 (with-tramp-file-property v localname "file-name-all-completions"
-           (let ((result '("./" "../")))
+           (let (result)
              ;; Get a list of directories and files.
 	     (dolist (item
 		      (tramp-gvfs-get-directory-attributes directory)

lisp/net/tramp.el

@@ -2742,19 +2742,27 @@ not in completion mode."
       (tramp-run-real-handler #'file-exists-p (list filename))))
 
 (defmacro tramp-skeleton-file-name-all-completions
-    (_filename _directory &rest body)
+    (filename directory &rest body)
   "Skeleton for `tramp-*-handle-filename-all-completions'.
 BODY is the backend specific code."
   (declare (indent 2) (debug t))
   `(ignore-error file-missing
      (delete-dups (delq nil
        (let* ((case-fold-search read-file-name-completion-ignore-case)
-	      (regexp (mapconcat #'identity completion-regexp-list "\\|"))
-	      (result ,@body))
+	      (result (progn ,@body)))
+	 ;; Some storage systems do not return "." and "..".
+	 (when (tramp-tramp-file-p ,directory)
+	   (dolist (elt '(".." "."))
+	     (when (string-prefix-p ,filename elt)
+	       (setq result (cons (concat elt "/") result)))))
 	 (if (consp completion-regexp-list)
 	     ;; Discriminate over `completion-regexp-list'.
 	     (mapcar
-	      (lambda (x) (and (stringp x) (string-match-p regexp x) x))
+	      (lambda (x)
+		(when (stringp x)
+		  (catch 'match
+		    (dolist (elt completion-regexp-list x)
+		      (unless (string-match-p elt x) (throw 'match nil))))))
 	      result)
 	   result))))))