(vc-switch-backend): Better error message if the buffer is not visiting a

file under version control.

diff --git a/lisp/vc.el b/lisp/vc.el
index 92d3979d084edf94435a1264ef195d9f55bebf1b..eb27390cea49830a461527ca819a833ff29b1637 100644 (file)
--- a/lisp/vc.el
+++ b/lisp/vc.el
@@ -2596,9 +2596,12 @@ By default, this command cycles through the registered backends.
 To get a prompt, use a prefix argument."
   (interactive
    (list
-    buffer-file-name
+    (or buffer-file-name
+        (error "There is no version-controlled file in this buffer"))
     (let ((backend (vc-backend buffer-file-name))
          (backends nil))
+      (unless backend
+        (error "File %s is not under version control" buffer-file-name))
       ;; Find the registered backends.
       (dolist (backend vc-handled-backends)
        (when (vc-call-backend backend 'registered buffer-file-name)