bug#15322: VC log buffer scrolls itself

[Dmitry Gutov <dgutov@yandex.ru>]

Richard Copley <rcopley@gmail.com> writes:

> ... perhaps I was going too far, but a fix is still needed to stop
> point jumping to the beginning of the buffer when working-revision is
> null (at least in Subversion). I suggest not calling
> `goto-location-func' or setting vc-sentinel-movepoint when
> working-revision is null, in `vc-print-log-internal'.
>
> I also suggest a null working-revision be passed by
> `vc-print-root-log', by the same argument Stefan used for
> `vc-print-log'.

Makes sense to me.

Unless someone objects, I'm going to install the following patch:

diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index bb4dd60..f64f42e 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -2224,8 +2224,9 @@ earlier revisions.  Show up to LIMIT entries (non-nil means unlimited)."
        (lambda (_bk _files-arg ret)
 	 (vc-print-log-setup-buttons working-revision
 				     is-start-revision limit ret))
-       (lambda (bk)
-	 (vc-call-backend bk 'show-log-entry working-revision))
+       (when working-revision
+         (lambda (bk)
+           (vc-call-backend bk 'show-log-entry working-revision)))
        (lambda (_ignore-auto _noconfirm)
 	 (vc-print-log-internal backend files working-revision
                               is-start-revision limit)))))
@@ -2263,8 +2264,10 @@ earlier revisions.  Show up to LIMIT entries (non-nil means unlimited)."
      (let ((inhibit-read-only t))
        (funcall setup-buttons-func backend files retval)
        (shrink-window-if-larger-than-buffer)
-       (funcall goto-location-func backend)
-       (setq vc-sentinel-movepoint (point))
+       ;; Bug#15322
+       (when goto-location-func
+         (funcall goto-location-func backend)
+         (setq vc-sentinel-movepoint (point)))
        (set-buffer-modified-p nil)))))
 
 (defun vc-incoming-outgoing-internal (backend remote-location buffer-name type)
@@ -2273,7 +2276,7 @@ earlier revisions.  Show up to LIMIT entries (non-nil means unlimited)."
    (lambda (bk buf type-arg _files)
      (vc-call-backend bk type-arg buf remote-location))
    (lambda (_bk _files-arg _ret) nil)
-   (lambda (_bk) (goto-char (point-min)))
+   nil
    (lambda (_ignore-auto _noconfirm)
      (vc-incoming-outgoing-internal backend remote-location buffer-name type))))
 
@@ -2328,16 +2331,15 @@ When called interactively with a prefix argument, prompt for LIMIT."
      (list (when (> vc-log-show-limit 0) vc-log-show-limit)))))
   (let ((backend (vc-deduce-backend))
 	(default-directory default-directory)
-	rootdir working-revision)
+	rootdir)
     (if backend
 	(setq rootdir (vc-call-backend backend 'root default-directory))
       (setq rootdir (read-directory-name "Directory for VC root-log: "))
       (setq backend (vc-responsible-backend rootdir))
       (unless backend
         (error "Directory is not version controlled")))
-    (setq working-revision (vc-working-revision rootdir)
-          default-directory rootdir)
-    (vc-print-log-internal backend (list rootdir) working-revision nil limit)))
+    (setq default-directory rootdir)
+    (vc-print-log-internal backend (list rootdir) nil nil limit)))
 
 ;;;###autoload
 (defun vc-log-incoming (&optional remote-location)