Use directory-files-no-dot-files-regexp wherever possible

Suggested by Paul Eggert.

* lisp/files.el (directory-files-no-dot-files-regexp):
Clarify semantics and purpose.
* lisp/dired.el (dired-re-no-dot):
Define as obsolete alias of directory-files-no-dot-files-regexp.
(dired-delete-file):
* lisp/gnus/gnus-util.el (gnus-delete-directory):
* lisp/net/ange-ftp.el (ange-ftp-delete-directory):
* lisp/obsolete/vc-arch.el (vc-arch-trim-revlib):
* lisp/org/ob-core.el (org-babel-remove-temporary-directory):
* lisp/vc/vc-rcs.el (vc-rcs-unregister):
Use directory-files-no-dot-files-regexp.

lisp/dired.el

@@ -3235,8 +3235,8 @@ Any other value means to ask for each directory."
 		 (const :tag "Confirm for each top directory only" top))
   :group 'dired)
 
-;; Match anything but `.' and `..'.
-(defvar dired-re-no-dot (rx (or (not ".") "...")))
+(define-obsolete-variable-alias 'dired-re-no-dot
+  'directory-files-no-dot-files-regexp "28.1")
 
 ;; Delete file, possibly delete a directory and all its files.
 ;; This function is useful outside of dired.  One could change its name
@@ -3258,7 +3258,9 @@ TRASH non-nil means to trash the file instead of deleting, provided
        ;; but more efficient
        (if (not (eq t (car (file-attributes file))))
            (delete-file file trash)
-         (let* ((empty-dir-p (null (directory-files file t dired-re-no-dot))))
+         (let* ((empty-dir-p (null (directory-files
+                                    file t
+                                    directory-files-no-dot-files-regexp))))
            (if (and recursive (not empty-dir-p))
                (unless (eq recursive 'always)
                  (let ((prompt

lisp/files.el

@@ -5754,7 +5754,10 @@ If called interactively, then PARENTS is non-nil."
 
 (defconst directory-files-no-dot-files-regexp
   "[^.]\\|\\.\\.\\."
-  "Regexp matching any file name except \".\" and \"..\".")
+  "Regexp matching any file name except \".\" and \"..\".
+More precisely, it matches parts of any nonempty string except those two.
+It is useful as the PATTERN argument to `directory-files' and
+`directory-files-and-attributes'.")
 
 (defun files--force (no-such fn &rest args)
   "Use NO-SUCH to affect behavior of function FN applied to list ARGS.

lisp/gnus/gnus-util.el

@@ -768,7 +768,7 @@ nil.  See also `gnus-bind-print-variables'."
 If there's no subdirectory, delete DIRECTORY as well."
   (when (file-directory-p directory)
     (let ((files (directory-files
-		  directory t (rx (or (not ".") "..."))))
+		  directory t directory-files-no-dot-files-regexp))
 	  file dir)
       (while files
 	(setq file (pop files))

lisp/gnus/gnus-uu.el

@@ -1674,7 +1674,7 @@ Gnus might fail to display all of it.")
     did-unpack))
 
 (defun gnus-uu-dir-files (dir)
-  (let ((dirs (directory-files dir t (rx (or (not ".") "..."))))
+  (let ((dirs (directory-files dir t directory-files-no-dot-files-regexp))
 	files file)
     (while dirs
       (if (file-directory-p (setq file (car dirs)))

lisp/net/ange-ftp.el

@@ -4169,8 +4169,7 @@ directory, so that Emacs will know its current contents."
 	       (if (file-directory-p file)
 		   (ange-ftp-delete-directory file recursive trash)
 		 (delete-file file trash)))
-	     ;; We do not want to delete "." and "..".
-	     (directory-files dir 'full (rx (or (not ".") "...")))))
+	     (directory-files dir 'full directory-files-no-dot-files-regexp)))
 	(if parsed
 	    (let* ((host (nth 0 parsed))
 		   (user (nth 1 parsed))

lisp/obsolete/vc-arch.el

@@ -597,20 +597,21 @@ CALLBACK expects (ENTRIES &optional MORE-TO-COME); see
     (unless (file-writable-p rl-dir)
       (error "No writable revlib directory found"))
     (message "Revlib at %s" rl-dir)
-    (let* ((archives (directory-files rl-dir 'full (rx (or (not ".") "..."))))
+    (let* ((archives (directory-files rl-dir 'full
+                                      directory-files-no-dot-files-regexp))
            (categories
             (apply 'append
                    (mapcar (lambda (dir)
                              (when (file-directory-p dir)
-                               (directory-files dir 'full
-                                                (rx (or (not ".") "...")))))
+                               (directory-files
+                                dir 'full directory-files-no-dot-files-regexp)))
                            archives)))
            (branches
             (apply 'append
                    (mapcar (lambda (dir)
                              (when (file-directory-p dir)
-                               (directory-files dir 'full
-                                                (rx (or (not ".") "...")))))
+                               (directory-files
+                                dir 'full directory-files-no-dot-files-regexp)))
                            categories)))
            (versions
             (apply 'append

lisp/org/ob-core.el

@@ -3053,9 +3053,8 @@ of `org-babel-temporary-directory'."
 		  (if (eq t (car (file-attributes file)))
 		      (delete-directory file)
 		    (delete-file file)))
-		;; We do not want to delete "." and "..".
 		(directory-files org-babel-temporary-directory 'full
-                                 (rx (or (not ".") "..."))))
+                                 directory-files-no-dot-files-regexp))
 	  (delete-directory org-babel-temporary-directory))
       (error
        (message "Failed to remove temporary Org-babel directory %s"

lisp/vc/vc-rcs.el

@@ -312,7 +312,7 @@ whether to remove it."
       (and (string= (file-name-nondirectory (directory-file-name dir)) "RCS")
 	   ;; check whether RCS dir is empty, i.e. it does not
 	   ;; contain any files except "." and ".."
-	   (not (directory-files dir nil (rx (or (not ".") "..."))))
+	   (not (directory-files dir nil directory-files-no-dot-files-regexp))
 	   (yes-or-no-p (format "Directory %s is empty; remove it? " dir))
 	   (delete-directory dir)))))