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, 6 insertions, 4 deletions

diff --git a/doc/lispref/buffers.texi b/doc/lispref/buffers.texi
index d8cf3d7919b..3e3b0bd9f01 100644
--- a/doc/lispref/buffers.texi
+++ b/doc/lispref/buffers.texi
@@ -541,10 +541,12 @@ file formerly visited.
 @ref{Text}.
 
 @defun buffer-modified-p &optional buffer
-This function returns @code{t} if the buffer @var{buffer} has been modified
-since it was last read in from a file or saved, or @code{nil}
-otherwise.  If @var{buffer} is not supplied, the current buffer
-is tested.
+This function returns non-@code{nil} if the buffer @var{buffer} has
+been modified since it was last read in from a file or saved, or
+@code{nil} otherwise.  If @var{buffer} has been autosaved after
+@var{buffer} was last modified, the symbol @code{autosaved} is
+returned.  If @var{buffer} is not supplied, the current buffer is
+tested.
 @end defun
 
 @defun set-buffer-modified-p flag