* lisp/vc/vc-annotate.el (vc-annotate-show-diff-revision-at-line-internal):

Use derived-mode-p.  Run the diff asynchronously.

1 files changed, 13 insertions, 15 deletions

diff --git a/lisp/vc/vc-annotate.el b/lisp/vc/vc-annotate.el
index a1dd807d828..f4964ef85cc 100644
--- a/lisp/vc/vc-annotate.el
+++ b/lisp/vc/vc-annotate.el
@@ -522,12 +522,12 @@ the file in question, search for the log entry required and move point."
 	     (car rev-at-line) t 1)))))))
 
 (defun vc-annotate-show-diff-revision-at-line-internal (filediff)
-  (if (not (equal major-mode 'vc-annotate-mode))
+  (if (not (derived-mode-p 'vc-annotate-mode))
       (message "Cannot be invoked outside of a vc annotate buffer")
     (let* ((rev-at-line (vc-annotate-extract-revision-at-line))
-	  (prev-rev nil)
-	  (rev (car rev-at-line))
-	  (fname (cdr rev-at-line)))
+           (prev-rev nil)
+           (rev (car rev-at-line))
+           (fname (cdr rev-at-line)))
       (if (not rev-at-line)
 	  (message "Cannot extract revision number from the current line")
 	(setq prev-rev
@@ -535,17 +535,15 @@ the file in question, search for the log entry required and move point."
                                (if filediff fname nil) rev))
 	(if (not prev-rev)
 	    (message "Cannot diff from any revision prior to %s" rev)
-	  (save-window-excursion
-	    (vc-diff-internal
-	     nil
-	     ;; The value passed here should follow what
-	     ;; `vc-deduce-fileset' returns.
-	     (list vc-annotate-backend
-		   (if filediff
-		       (list fname)
-		     nil))
-	     prev-rev rev))
-	  (switch-to-buffer "*vc-diff*"))))))
+          (vc-diff-internal
+           t
+           ;; The value passed here should follow what
+           ;; `vc-deduce-fileset' returns.
+           (list vc-annotate-backend
+                 (if filediff
+                     (list fname)
+                   nil))
+           prev-rev rev))))))
 
 (defun vc-annotate-show-diff-revision-at-line ()
   "Visit the diff of the revision at line from its previous revision."