(vc-switch-backend): Signal an error if the file is not registered

under the new backend.

diff --git a/lisp/vc.el b/lisp/vc.el
index b298831cb1b3227e15fc018987b661d74df530ed..4dba0fea2ae32c676834520366ca746c7e72d745 100644 (file)
--- a/lisp/vc.el
+++ b/lisp/vc.el
@@ -2190,6 +2190,8 @@ VC's perspective on FILE, it does not register or unregister it."
    (list
     buffer-file-name
     (intern (upcase (read-string "Switch to backend: ")))))
+  (unless (vc-call-backend backend 'registered file)
+    (error "%s is not registered in %s" file backend))
   (vc-file-clearprops file)
   (vc-file-setprop file 'vc-backend backend)
   (vc-resynch-buffer file t t))