bug#11757: Acknowledgement (24.1.50; vc-git calls `process-file' too many times)

[Dmitry Gutov]

On 30.06.2012 13:03, Michael Albinus wrote:
> Dmitry Gutov <dgutov@yandex.ru> writes:
>
> > On 29.06.2012 20:40, Michael Albinus wrote:
> > > > > A stale cache is bad, of course. We must carefully check, where a cached
> > > > > value has to be invalidated. But why should vc-working-revision being
> > > > > invalidated after saving? It is still the same, I believe. Switching to
> > > > > another branch shall be observed by Emacs, 'cause there is another
> > > > > version of the file on the disk, and Emacs warns you before editing.
> > > >
> > > > This won't happen in following cases:
> > > > 1) We switch to revision when the opened file is the same.
> > > > 2) It doesn't exist there.
> > > > 3) We just delete it from disk from outside of Emacs.
> > > > So the file isn't changed, and you see no warning or update, even
> > > > after you write it to disk from Emacs again.
> > >
> > > I see. Maybe we find a hook, where we could invalidate the vc cache when
> > > a file is written which does not exist on the disk?
> >
> > (vc-before-save) might be the place to do that.
>
> In vc-after-save, vc-git-state is called. Wouldn't it be sufficient to
> invalidate the cache there, when it detects that the file is not up-to-date?

Why there? Problem with working-revision is common for all backends, as 
far as I can see.

Also, how? After the file is written, we can't check if it didn't exist 
on disk anymore.

Here's what I had in mind:

diff --git a/lisp/vc/vc-hooks.el b/lisp/vc/vc-hooks.el
index bba7217..4bff5fc 100644
--- a/lisp/vc/vc-hooks.el
+++ b/lisp/vc/vc-hooks.el
@@ -703,7 +703,9 @@ Before doing that, check if there are any old 
backups and get rid of them."
   ;; another name.  This enables local diffs and local reverting.
   (let ((file buffer-file-name)
         backend)
-    (ignore-errors               ;Be careful not to prevent saving the 
file.
+    (ignore-errors      ;Be careful not to prevent saving the file.
+      (unless (file-exists-p file)
+        (vc-file-clearprops file))
       (and (setq backend (vc-backend file))
            (vc-up-to-date-p file)
            (eq (vc-checkout-model backend (list file)) 'implicit)