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.

2 files changed, 12 insertions, 0 deletions

diff --git a/doc/emacs/entering.texi b/doc/emacs/entering.texi
index 66817e3067f..09331e80fb1 100644
--- a/doc/emacs/entering.texi
+++ b/doc/emacs/entering.texi
@@ -133,6 +133,11 @@ run.  One convenient function to use as the value of
 @code{confirm-kill-emacs} is the function @code{yes-or-no-p}.  The
 default value of @code{confirm-kill-emacs} is @code{nil}.
 
+@vindex confirm-kill-processes
+  If the value of the variable @code{confirm-kill-processes} is
+@code{nil}, @kbd{C-x C-c} does not ask for confirmation before killing
+subprocesses started by Emacs.  The value is @code{t} by default.
+
   To further customize what happens when Emacs is exiting, see
 @ref{Killing Emacs,,, elisp, The GNU Emacs Lisp Reference Manual}.
 
diff --git a/doc/lispref/processes.texi b/doc/lispref/processes.texi
index f9d5096dbea..87c0b5c7687 100644
--- a/doc/lispref/processes.texi
+++ b/doc/lispref/processes.texi
@@ -1970,6 +1970,13 @@ shell process to avoid querying:
 @end smallexample
 @end defun
 
+@defopt confirm-kill-processes
+If this user option is set to @code{t} (the default), then Emacs asks
+for confirmation before killing processes on exit.  If it is
+@code{nil}, Emacs kills processes without confirmation, i.e., the
+query flag of all processes is ignored.
+@end defopt
+
 @node System Processes
 @section Accessing Other Processes
 @cindex system processes