(after-find-file): When visiting a backup file, make it read-only.

1 files changed, 5 insertions, 1 deletions

diff --git a/lisp/files.el b/lisp/files.el
index ee56e4d3bf2..144d79da28e 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -1189,7 +1189,7 @@ unless NOMODES is non-nil."
            (msg
             (cond ((and error (file-attributes buffer-file-name))
                    (setq buffer-read-only t)
-                   "File exists, but cannot be read.")
+                   "File exists, but cannot be read")
                   ((not buffer-read-only)
                    (if (and warn
                             (file-newer-than-file-p (make-auto-save-file-name)
@@ -1216,6 +1216,10 @@ unless NOMODES is non-nil."
             (or not-serious (sit-for 1 nil t)))))
     (if (and auto-save-default (not noauto))
         (auto-save-mode t)))
+  ;; Make people do a little extra work (C-x C-q)
+  ;; before altering a backup file.
+  (if (backup-file-name-p buffer-file-name)
+      (setq buffer-read-only t))
   (if nomodes
       nil
     (and view-read-only view-mode