Add a new command `restart-emacs'

* doc/lispref/os.texi (Killing Emacs): Document it.

* lisp/files.el (save-buffers-kill-emacs): Add new RESTART parameter.
(restart-emacs): New function.

* src/emacs.c (terminate_due_to_signal, Fkill_emacs): Take an
optional RESTART parameter.

* test/lisp/files-tests.el
(files-tests-save-buffers-kill-emacs--confirm-kill-processes):
* src/xterm.c (x_connection_closed):
* src/xsmfns.c (Fhandle_save_session):
* src/keyboard.c (Fcommand_error_default_function, command_loop)
(command_loop_1, read_menu_command, read_event_from_main_queue)
(read_key_sequence, quit_throw_to_read_char):
* src/eval.c (process_quit_flag): Adjust Fkill_emacs callers.

1 files changed, 12 insertions, 1 deletions

diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi
index 8366689640f..eea0ab8f6bc 100644
--- a/doc/lispref/os.texi
+++ b/doc/lispref/os.texi
@@ -699,7 +699,7 @@ If you started Emacs from a terminal, the parent process normally
 resumes control.  The low-level primitive for killing Emacs is
 @code{kill-emacs}.
 
-@deffn Command kill-emacs &optional exit-data
+@deffn Command kill-emacs &optional exit-data restart
 This command calls the hook @code{kill-emacs-hook}, then exits the
 Emacs process and kills it.
 
@@ -714,6 +714,10 @@ input) can read them.
 If @var{exit-data} is neither an integer nor a string, or is omitted,
 that means to use the (system-specific) exit status which indicates
 successful program termination.
+
+If @var{restart} is non-@code{nil}, instead of just exiting at the
+end, start a new Emacs process, using the same command line arguments
+as the currently running Emacs process.
 @end deffn
 
 @cindex SIGTERM
@@ -756,6 +760,13 @@ the remaining functions in this hook.  Calling @code{kill-emacs}
 directly does not run this hook.
 @end defopt
 
+@deffn Command restart-emacs
+This command does the same as @code{save-buffers-kill-emacs}, but
+instead of just killing the current Emacs process at the end, it'll
+restart a new Emacs process, using the same command line arguments as
+the currently running Emacs process.
+@end deffn
+
 @node Suspending Emacs
 @subsection Suspending Emacs
 @cindex suspending Emacs