Make querying to kill processes customizable

Introduce a new customization option, `confirm-kill-processes', that
users can set to nil if they don't want Emacs to nag them about killing
processes.

* lisp/files.el (confirm-kill-processes): New customization option.
(save-buffers-kill-emacs): Use customization option.

* test/lisp/files-tests.el
(files-test--save-buffers-kill-emacs--confirm-kill-processes): Add
test for new customization option.

* doc/emacs/entering.texi (Exiting): Document new user option.

* doc/lispref/processes.texi (Query Before Exit): Document new
user option.

* etc/NEWS: Document new user option.

1 files changed, 23 insertions, 0 deletions

diff --git a/test/lisp/files-tests.el b/test/lisp/files-tests.el
index 479848abb23..80d5e5befbc 100644
--- a/test/lisp/files-tests.el
+++ b/test/lisp/files-tests.el
@@ -197,5 +197,28 @@ form.")
       (setenv "FOO" foo-env)
       (setenv "BAR" bar-env))))
 
+(ert-deftest files-test--save-buffers-kill-emacs--confirm-kill-processes ()
+  "Test that `save-buffers-kill-emacs' honors
+`confirm-kill-processes'."
+  (cl-letf* ((yes-or-no-p-prompts nil)
+             ((symbol-function #'yes-or-no-p)
+              (lambda (prompt)
+                (push prompt yes-or-no-p-prompts)
+                nil))
+             (kill-emacs-args nil)
+             ((symbol-function #'kill-emacs)
+              (lambda (&optional arg) (push arg kill-emacs-args)))
+             (process
+              (make-process
+               :name "sleep"
+               :command (list
+                         (expand-file-name invocation-name invocation-directory)
+                         "-batch" "-Q" "-eval" "(sleep-for 1000)")))
+             (confirm-kill-processes nil))
+    (save-buffers-kill-emacs)
+    (kill-process process)
+    (should-not yes-or-no-p-prompts)
+    (should (equal kill-emacs-args '(nil)))))
+
 (provide 'files-tests)
 ;;; files-tests.el ends here