Add safe-local-variable-directories variable.

This variable can be set to automatically load risky dir-local
variables from a list of trusted directories.

* lisp/emacs-lisp/files.el (safe-local-variable-directories,
hack-local-variables-filter, hack-local-variables-confirm): New
variable and associated logic.
* test/lisp/files-tests.el
(files-tests-safe-local-variable-directories): Add tests for same.
* doc/emacs/custom.texi (Safe File Variables): Add documentation for
same.
* doc/lispref/variables.texi (File Local Variables): Add documentation
for same.
* etc/NEWS (Lisp Changes in Emacs 30.1): Add news entry for
same.  (Bug#61901)

1 files changed, 21 insertions, 0 deletions

diff --git a/test/lisp/files-tests.el b/test/lisp/files-tests.el
index aadb60e1de7..e87bb3cfa0a 100644
--- a/test/lisp/files-tests.el
+++ b/test/lisp/files-tests.el
@@ -166,6 +166,27 @@ form.")
       (hack-local-variables)
       (should (eq lexical-binding nil)))))
 
+(ert-deftest files-tests-safe-local-variable-directories ()
+  ;; safe-local-variable-directories should be risky,
+  ;; so use it as an arbitrary risky variable.
+  (let ((test-alist '((safe-local-variable-directories . "some_val")))
+        (fakedir "/test1/test2/")
+        (enable-local-eval t))
+    (with-temp-buffer
+      (setq safe-local-variable-directories (list fakedir))
+      (hack-local-variables-filter test-alist fakedir)
+      (should (equal file-local-variables-alist test-alist)))
+    (with-temp-buffer
+      (setq safe-local-variable-directories (list fakedir))
+      (setq noninteractive t)
+      (hack-local-variables-filter test-alist "wrong")
+      (should-not (equal file-local-variables-alist test-alist)))
+    (with-temp-buffer
+      (setq safe-local-variable-directories '())
+      (setq noninteractive t)
+      (hack-local-variables-filter test-alist fakedir)
+      (should-not (equal file-local-variables-alist test-alist)))))
+
 (defvar files-test-bug-18141-file
   (ert-resource-file "files-bug18141.el.gz")
   "Test file for bug#18141.")