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, 35 insertions, 0 deletions

diff --git a/test/src/buffer-tests.el b/test/src/buffer-tests.el
index c1e5d0ebed3..10dac68f9fe 100644
--- a/test/src/buffer-tests.el
+++ b/test/src/buffer-tests.el
@@ -1482,4 +1482,39 @@ with parameters from the *Messages* buffer modification."
           (when auto-save
             (ignore-errors (delete-file auto-save))))))))
 
+(ert-deftest test-buffer-modifications ()
+  (ert-with-temp-file file
+    (with-current-buffer (find-file file)
+      (auto-save-mode 1)
+      (should-not (buffer-modified-p))
+      (insert "foo")
+      (should (buffer-modified-p))
+      (should-not (eq (buffer-modified-p) 'autosaved))
+      (do-auto-save nil t)
+      (should (eq (buffer-modified-p) 'autosaved))
+      (with-silent-modifications
+        (put-text-property 1 3 'face 'bold))
+      (should (eq (buffer-modified-p) 'autosaved))
+      (save-buffer)
+      (should-not (buffer-modified-p))
+      (with-silent-modifications
+        (put-text-property 1 3 'face 'italic))
+      (should-not (buffer-modified-p)))))
+
+(ert-deftest test-restore-buffer-modified-p ()
+  (ert-with-temp-file file
+    (with-current-buffer (find-file file)
+      (auto-save-mode 1)
+      (should-not (buffer-modified-p))
+      (insert "foo")
+      (should (buffer-modified-p))
+      (restore-buffer-modified-p nil)
+      (should-not (buffer-modified-p))
+      (insert "bar")
+      (do-auto-save nil t)
+      (should (eq (buffer-modified-p) 'autosaved))
+      (insert "zot")
+      (restore-buffer-modified-p 'autosaved)
+      (should (eq (buffer-modified-p) 'autosaved)))))
+
 ;;; buffer-tests.el ends here