Reimplement recent with-silent-modifications auto-save changes

* doc/lispref/buffers.texi (Buffer Modification): Document
buffer-modified-p returning `autosaved'.
* lisp/subr.el (with-silent-modifications): Use
restore-buffer-modified-p instead of altering the buffer modiff
(since this has other side effects like not updating after async
`display' changes.

* src/buffer.c (Fbuffer_modified_p): Allow returning whether the
buffer has been autosaved after changes.
(Frestore_buffer_modified_p): Allow adjusting whether the buffer
has been autosaved after changes.

* src/fileio.c (Fdo_auto_save): Refill the doc string.

1 files changed, 4 insertions, 8 deletions

diff --git a/lisp/subr.el b/lisp/subr.el
index 01549cc6f74..54c9f35264d 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -4594,21 +4594,17 @@ like `buffer-modified-p', checking whether the file is locked by
 someone else, running buffer modification hooks, and other things
 of that nature."
   (declare (debug t) (indent 0))
-  (let ((modified (make-symbol "modified"))
-        (tick (make-symbol "tick")))
+  (let ((modified (make-symbol "modified")))
     `(let* ((,modified (buffer-modified-p))
-            (,tick (buffer-modified-tick))
             (buffer-undo-list t)
             (inhibit-read-only t)
             (inhibit-modification-hooks t))
        (unwind-protect
            (progn
              ,@body)
-         ;; We restore the buffer tick count, too, because otherwise
-         ;; we'll trigger a new auto-save.
-         (internal--set-buffer-modified-tick ,tick)
-         (unless ,modified
-           (restore-buffer-modified-p nil))))))
+         (when (or (not ,modified)
+                   (eq ,modified 'autosaved))
+           (restore-buffer-modified-p ,modified))))))
 
 (defmacro with-output-to-string (&rest body)
   "Execute BODY, return the text it sent to `standard-output', as a string."