Port file-system-info to non-Microsoft

* admin/merge-gnulib (GNULIB_MODULES): Add fsusage.
* doc/emacs/files.texi (Directories): Remove documentation of
now-obsolete directory-free-space-program and
directory-free-space-args.
* etc/NEWS: Mention change.
* etc/PROBLEMS: Slow df is no longer a problem.
* lib/fsusage.c, lib/fsusage.h, m4/fsusage.m4:
New files, copied from Gnulib.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* lisp/dired.el (dired-free-space-program)
(dired-free-space-args): These aliases are now obsolete.
* lisp/files.el (directory-free-space-program)
(directory-free-space-args): Now obsolete.
(get-free-disk-space): Just call file-system-info instead
of the now-obsolete directory-free-space-program.
* nt/gnulib-cfg.mk (OMIT_GNULIB_MODULE_fsusage): New macro.
* src/fileio.c: Include fsusage.h.
(blocks_to_bytes, Ffile_system_info) [!DOS_NT]: New functions.
(syms_of_fileio) [!DOS_NT]: Defsubr file-system-info.

2 files changed, 16 insertions, 39 deletions

diff --git a/lisp/dired.el b/lisp/dired.el
index 9e09d349f7c..1ec3ac4f99c 100644
--- a/lisp/dired.el
+++ b/lisp/dired.el
@@ -198,8 +198,10 @@ The target is used in the prompt for file copy, rename etc."
 
 ; These variables were deleted and the replacements are on files.el.
 ; We leave aliases behind for back-compatibility.
-(defvaralias 'dired-free-space-program 'directory-free-space-program)
-(defvaralias 'dired-free-space-args 'directory-free-space-args)
+(define-obsolete-variable-alias 'dired-free-space-program
+  'directory-free-space-program "27.1")
+(define-obsolete-variable-alias 'dired-free-space-args
+  'directory-free-space-args "27.1")
 
 ;;; Hook variables
 
diff --git a/lisp/files.el b/lisp/files.el
index 336bbc8648d..194c87ab680 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -6386,58 +6386,33 @@ if you want to specify options, use `directory-free-space-args'.
 
 A value of nil disables this feature.
 
-If the function `file-system-info' is defined, it is always used in
-preference to the program given by this variable."
+This variable is obsolete; Emacs no longer uses it."
   :type '(choice (string :tag "Program") (const :tag "None" nil))
   :group 'dired)
+(make-obsolete-variable 'directory-free-space-program
+                        "ignored, as Emacs uses `file-system-info' instead"
+                        "27.1")
 
 (defcustom directory-free-space-args
   (purecopy (if (eq system-type 'darwin) "-k" "-Pk"))
   "Options to use when running `directory-free-space-program'."
   :type 'string
   :group 'dired)
+(make-obsolete-variable 'directory-free-space-args
+                        "ignored, as Emacs uses `file-system-info' instead"
+                        "27.1")
 
 (defun get-free-disk-space (dir)
   "Return the amount of free space on directory DIR's file system.
 The return value is a string describing the amount of free
 space (normally, the number of free 1KB blocks).
 
-This function calls `file-system-info' if it is available, or
-invokes the program specified by `directory-free-space-program'
-and `directory-free-space-args'.  If the system call or program
-is unsuccessful, or if DIR is a remote directory, this function
-returns nil."
+If DIR's free space cannot be obtained, or if DIR is a remote
+directory, this function returns nil."
   (unless (file-remote-p (expand-file-name dir))
-    ;; Try to find the number of free blocks.  Non-Posix systems don't
-    ;; always have df, but might have an equivalent system call.
-    (if (fboundp 'file-system-info)
-        (let ((fsinfo (file-system-info dir)))
-          (if fsinfo
-              (format "%.0f" (/ (nth 2 fsinfo) 1024))))
-      (setq dir (expand-file-name dir))
-      (save-match-data
-        (with-temp-buffer
-          (when (and directory-free-space-program
-                     ;; Avoid failure if the default directory does
-                     ;; not exist (Bug#2631, Bug#3911).
-                     (let ((default-directory
-                             (locate-dominating-file dir 'file-directory-p)))
-                       (eq (process-file directory-free-space-program
-                                         nil t nil
-                                         directory-free-space-args
-                                         (file-relative-name dir))
-                           0)))
-            ;; Assume that the "available" column is before the
-            ;; "capacity" column.  Find the "%" and scan backward.
-            (goto-char (point-min))
-            (forward-line 1)
-            (when (re-search-forward
-                   "[[:space:]]+[^[:space:]]+%[^%]*$"
-                   (line-end-position) t)
-              (goto-char (match-beginning 0))
-              (let ((endpt (point)))
-                (skip-chars-backward "^[:space:]")
-                (buffer-substring-no-properties (point) endpt)))))))))
+    (let ((avail (nth 2 (file-system-info dir))))
+      (if avail
+          (format "%.0f" (/ avail 1024))))))
 
 ;; The following expression replaces `dired-move-to-filename-regexp'.
 (defvar directory-listing-before-filename-regexp