bug#2623: 23.0.91; File is under version-control; use C-x v v to check in/out

On 2009-03-12 00:39 +0000, Stefan Monnier wrote:
>>>>> BTW, why did you type C-x C-q?  Is the file read-only?
>>>> Sometimes I turn the file into read-only before showing to other people
>>>> in case they accidentally type something into it.
>>> I see, so in this case we could probably avoid the message by being
>>> a bit more clever (e.g. don't show the message if it's not the first
>>> time C-x C-q is used in this buffer).
>> There is difference between turning the buffer into read-only and the
>> file on disk being read-only. VC backends depend on the latter for their
>> status based on my experience with RCS. So showing such a message does
>
> No, actually VC did make buffers read-only based on the backend's
> status rather than just based on the file's own read-onlyness.  And
> C-x C-q was used by many people as the main way to interact with VC
> (both to check out and to check back in).  I know it all sounds really
> odd seen from today's point of view, but it still made sense in
> Emacs-21, which isn't that old.

The message is wrong when the underlying vc backend does not use such a
backward mechanism. However, toggle-read-only unconditionally show this
message.

This situation can be improved by a one line change:

--- /tmp/emacs/share/emacs/23.0.60/lisp/files.el.gz
+++ /tmp/buffer-content-32645B0g
@@ -4429,7 +4429,7 @@
       (view-mode-enter))
      (t (setq buffer-read-only (not buffer-read-only))
         (force-mode-line-update)))
-    (if (vc-backend buffer-file-name)
+    (if (memq (vc-backend buffer-file-name) '(RCS SCCS))
         (message "%s" (substitute-command-keys
                   (concat "File is under version-control; "
                           "use \\[vc-next-action] to check in/out"))))))

Diff finished.  Thu Mar 12 17:56:16 2009

I have no idea whether SCCS uses read-only mechanism tho. But it is
better to delete this 'message' from toggle-read-only. It looks out of
place and it is not even documented in the doc string.

I am curious how would C-x C-q have anything to do with vc. Even when
using RCS backend, it never is part of the work flow.

>         Stefan

-- 
.:  Leo  :.  [ sdl.web AT gmail.com ]  .: I use Emacs :.

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