(select-safe-coding-system): Don't offer coding systems that use locking shift.

Ask for confirmation if chosen coding system disagrees with
a `coding:' spec in the file.

1 files changed, 27 insertions, 1 deletions

diff --git a/lisp/international/mule-cmds.el b/lisp/international/mule-cmds.el
index ed11d69fb9b..453f53fb126 100644
--- a/lisp/international/mule-cmds.el
+++ b/lisp/international/mule-cmds.el
@@ -636,6 +636,16 @@ and TO is ignored."
               (setcar l mime-charset))
           (setq l (cdr l))))
 
+      ;; Don't offer variations with locking shift, which you
+      ;; basically never want.
+      (let (l)
+        (dolist (elt codings (setq codings (nreverse l)))
+          (unless (or (eq 'coding-category-iso-7-else
+                          (coding-system-category elt))
+                      (eq 'coding-category-iso-8-else
+                          (coding-system-category elt)))
+            (push elt l))))
+
       ;; Make sure the offending buffer is displayed.
       (or (stringp from)
           (pop-to-buffer bufname))
@@ -705,7 +715,23 @@ and TO is ignored."
 
     (if (eq coding-system t)
         (setq coding-system buffer-file-coding-system))
-    coding-system))
+    ;; Check we're not inconsistent with what `coding:' spec &c would
+    ;; give when file is re-read.
+    (unless (stringp from)
+      (let ((auto-cs (save-restriction
+                       (widen)
+                       (save-excursion
+                         (goto-char (point-min))
+                         (set-auto-coding (or buffer-file-name "")
+                                          (buffer-size))))))
+        (if (and auto-cs
+                 (not (coding-system-equal (coding-system-base coding-system)
+                                           (coding-system-base auto-cs))))
+            (unless (yes-or-no-p
+                     (format "Selected encoding %s disagrees with \
+%s specified by file contents.  Really save (else edit coding cookies \
+and try again)? " coding-system auto-cs))
+              (error "Save aborted")))))    coding-system))
 
 (setq select-safe-coding-system-function 'select-safe-coding-system)