Add `enable-dir-local-variables'

* lisp/files.el (enable-dir-local-variables): New variable.
(hack-dir-local-variables): Respect enable-dir-local-variables.

* lisp/tutorial.el (help-with-tutorial): Ignore directory-local variables.

Fixes: debbugs:11127

etc/NEWS

@@ -45,6 +45,10 @@ non-nil, they output the same results.
 ** `eval-defun' on an already defined defcustom calls the :set function,
 if there is one.
 
+** If the new variable `enable-dir-local-variables' is nil,
+directory local variables are ignored.  May be useful for some modes
+that want to ignore directory-locals while still respecting file-locals.
+
 ** The option `set-mark-default-inactive' has been deleted.
 This unfinished feature was introduced by accident in Emacs 23.1;
 simply disabling Transient Mark mode does the same thing.
@@ -228,7 +232,7 @@ alist of extended attributes as returned by the new function
 file using `set-file-extended-attributes'.
 
 
-* Lisp changes in Emacs 24.4
+* Lisp Changes in Emacs 24.4
 
 ** Support for filesystem notifications.
 Emacs now supports notifications of filesystem changes, such as
@@ -273,7 +277,7 @@ used in place of the 9th element of `file-attributes'.
 and ACL entries.
 
 
-* Changes in Emacs 24.4 on non-free operating systems
+* Changes in Emacs 24.4 on Non-Free Operating Systems
 
 +++
 ** The "generate a backtrace on fatal error" feature now works on MS Windows.

lisp/ChangeLog

 2013-02-11  Glenn Morris  <rgm@gnu.org>
+	* files.el (enable-dir-local-variables): New variable.
+	(hack-dir-local-variables): Respect enable-dir-local-variables.
+	* tutorial.el (help-with-tutorial):
+	Ignore directory-local variables.  (Bug#11127)
+
 	* vc/vc-svn.el (vc-svn-command): Move --non-interactive from here...
 	(vc-svn-global-switches): ... to here.  (Bug#13513)

lisp/files.el

@@ -507,6 +507,11 @@ and ignores this variable."
 		 (other :tag "Query" other))
   :group 'find-file)
 
+(defvar enable-dir-local-variables t
+  "Non-nil means enable use of directory-local variables.
+Some modes may wish to set this to nil to prevent directory-local
+settings being applied, but still respect file-local ones.")
+
 ;; This is an odd variable IMO.
 ;; You might wonder why it is needed, when we could just do:
 ;; (set (make-local-variable 'enable-local-variables) nil)
@@ -3659,8 +3664,12 @@ is found.  Returns the new class name."
 (defun hack-dir-local-variables ()
   "Read per-directory local variables for the current buffer.
 Store the directory-local variables in `dir-local-variables-alist'
-and `file-local-variables-alist', without applying them."
+and `file-local-variables-alist', without applying them.
+
+This does nothing if either `enable-local-variables' or
+`enable-dir-local-variables' are nil."
   (when (and enable-local-variables
+	     enable-dir-local-variables
 	     (or enable-remote-dir-locals
 		 (not (file-remote-p (or (buffer-file-name)
 					 default-directory)))))

lisp/tutorial.el

@@ -829,10 +829,9 @@ Run the Viper tutorial? "))
             (progn
               (insert-file-contents (tutorial--saved-file))
 	      (let ((enable-local-variables :safe)
-                    (enable-local-eval nil))
+                    (enable-local-eval nil)
+                    (enable-dir-local-variables nil)) ; bug#11127
 		(hack-local-variables))
-              ;; FIXME?  What we actually want is to ignore dir-locals (?).
-              (setq buffer-read-only nil) ; bug#11118
               (goto-char (point-min))
               (setq old-tut-point
                     (string-to-number
@@ -849,10 +848,9 @@ Run the Viper tutorial? "))
               (setq tutorial--point-before-chkeys (point-marker)))
           (insert-file-contents (expand-file-name filename tutorial-directory))
 	  (let ((enable-local-variables :safe)
-                (enable-local-eval nil))
+                (enable-local-eval nil)
+                (enable-dir-local-variables nil)) ; bug#11127
 	    (hack-local-variables))
-          ;; FIXME?  What we actually want is to ignore dir-locals (?).
-          (setq buffer-read-only nil) ; bug#11118
           (forward-line)
           (setq tutorial--point-before-chkeys (point-marker)))