New commands to create an empty file

Similarly as `create-directory', `dired-create-directory',
the new commands create the parent dirs as needed (Bug#24150).
* lisp/files.el (make-empty-file): New command.

* lisp/dired-aux.el (dired-create-empty-file): New command.
(dired--find-topmost-parent-dir): New function extracted
from `dired-create-directory'.
(dired-create-directory, dired-create-empty-file): Use it.

* lisp/dired.el (dired-mode-map):
Add menu entry for `dired-create-empty-file'.

* doc/emacs/dired.texi (Misc Dired Features)
* doc/lispref/files.texi (Create/Delete Dirs): Update manual.
; * etc/NEWS: Announce the changes.

doc/emacs/dired.texi

@@ -1468,6 +1468,11 @@ rotation is lossless, and uses an external utility called
 directory's name, and creates that directory.  It signals an error if
 the directory already exists.
 
+@findex dired-create-empty-file
+  The command (@code{dired-create-empty-file}) reads a
+file name, and creates that file.  It signals an error if
+the file already exists.
+
 @cindex searching multiple files via Dired
 @kindex M-s a C-s @r{(Dired)}
 @kindex M-s a M-C-s @r{(Dired)}

doc/lispref/files.texi

@@ -3005,10 +3005,16 @@ This command creates a directory named @var{dirname}.  If
 @var{parents} is non-@code{nil}, as is always the case in an
 interactive call, that means to create the parent directories first,
 if they don't already exist.
-
 @code{mkdir} is an alias for this.
 @end deffn
 
+@deffn Command make-empty-file filename &optional parents
+This command creates an empty file named @var{filename}.
+As @code{make-directory}, this command creates parent directories
+if @var{parents} is non-@code{nil}.
+If @var{filename} already exists, this command signals an error.
+@end deffn
+
 @deffn Command copy-directory dirname newname &optional keep-time parents copy-contents
 This command copies the directory named @var{dirname} to
 @var{newname}.  If @var{newname} is a directory name,

etc/NEWS

@@ -185,6 +185,9 @@ This triggers to search the program on the remote host as indicated by
 
 * Editing Changes in Emacs 27.1
 
++++
+** New command 'make-empty-file'.
+
 ---
 ** New variable 'x-wait-for-event-timeout'.
 This controls how long Emacs will wait for updates to the graphical
@@ -222,6 +225,11 @@ navigation and editing of large files.
 
 * Changes in Specialized Modes and Packages in Emacs 27.1
 
++++
+** Dired
+
+*** New command 'dired-create-empty-file'.
+
 ** Change Logs and VC
 
 *** Recording ChangeLog entries doesn't require an actual file.

lisp/dired-aux.el

@@ -1989,6 +1989,19 @@ Optional arg HOW-TO determines how to treat the target.
       dired-dirs)))
 
 
+
+;; We use this function in `dired-create-directory' and
+;; `dired-create-empty-file'; the return value is the new entry
+;; in the updated Dired buffer.
+(defun dired--find-topmost-parent-dir (filename)
+  "Return the topmost nonexistent parent dir of FILENAME.
+FILENAME is a full file name."
+  (let ((try filename) new)
+    (while (and try (not (file-exists-p try)) (not (equal new try)))
+      (setq new try
+	    try (directory-file-name (file-name-directory try))))
+    new))
+
 ;;;###autoload
 (defun dired-create-directory (directory)
   "Create a directory called DIRECTORY.
@@ -1997,18 +2010,32 @@ If DIRECTORY already exists, signal an error."
   (interactive
    (list (read-file-name "Create directory: " (dired-current-directory))))
   (let* ((expanded (directory-file-name (expand-file-name directory)))
-	 (try expanded) new)
+	 new)
     (if (file-exists-p expanded)
 	(error "Cannot create directory %s: file exists" expanded))
-    ;; Find the topmost nonexistent parent dir (variable `new')
-    (while (and try (not (file-exists-p try)) (not (equal new try)))
-      (setq new try
-	    try (directory-file-name (file-name-directory try))))
+    (setq new (dired--find-topmost-parent-dir expanded))
     (make-directory expanded t)
     (when new
       (dired-add-file new)
       (dired-move-to-filename))))
 
+;;;###autoload
+(defun dired-create-empty-file (file)
+  "Create an empty file called FILE.
+ Add a new entry for the new file in the Dired buffer.
+ Parent directories of FILE are created as needed.
+ If FILE already exists, signal an error."
+  (interactive (list (read-file-name "Create empty file: ")))
+  (let* ((expanded (expand-file-name file))
+         new)
+    (if (file-exists-p expanded)
+        (error "Cannot create file %s: file exists" expanded))
+    (setq new (dired--find-topmost-parent-dir expanded))
+    (make-empty-file file 'parents)
+    (when new
+      (dired-add-file new)
+      (dired-move-to-filename))))
+
 (defun dired-into-dir-with-symlinks (target)
   (and (file-directory-p target)
        (not (file-symlink-p target))))

lisp/dired.el

@@ -1802,6 +1802,9 @@ Do so according to the former subdir alist OLD-SUBDIR-ALIST."
     (define-key map [menu-bar immediate create-directory]
       '(menu-item "Create Directory..." dired-create-directory
 		  :help "Create a directory"))
+    (define-key map [menu-bar immediate create-empty-file]
+      '(menu-item "Create Empty file..." dired-create-empty-file
+		  :help "Create an empty file"))
     (define-key map [menu-bar immediate wdired-mode]
       '(menu-item "Edit File Names" wdired-change-to-wdired-mode
 		  :help "Put a Dired buffer in a mode in which filenames are editable"

lisp/files.el

@@ -5519,6 +5519,21 @@ raised."
 	  (dolist (dir create-list)
             (files--ensure-directory dir)))))))
 
+(defun make-empty-file (filename &optional parents)
+  "Create an empty file FILENAME.
+Optional arg PARENTS, if non-nil then creates parent dirs as needed.
+
+If called interactively, then PARENTS is non-nil."
+  (interactive
+   (let ((filename (read-file-name "Create empty file: ")))
+     (list filename t)))
+  (when (and (file-exists-p filename) (null parents))
+    (signal 'file-already-exists `("File exists" ,filename)))
+  (let ((paren-dir (file-name-directory filename)))
+    (when (and paren-dir (not (file-exists-p paren-dir)))
+      (make-directory paren-dir parents)))
+  (write-region "" nil filename nil 0))
+
 (defconst directory-files-no-dot-files-regexp
   "^\\([^.]\\|\\.\\([^.]\\|\\..\\)\\).*"
   "Regexp matching any file name except \".\" and \"..\".")