New option, detach-on-destroy, to set what happens to a client when the session

it is attached to is destroyed. If on (the default), it is detached; if off, it
is switched to the most recently active session.

cmd-set-option.c

@@ -87,6 +87,7 @@ const struct set_option_entry set_session_option_table[] = {
 	{ "default-path", SET_OPTION_STRING, 0, 0, NULL },
 	{ "default-shell", SET_OPTION_STRING, 0, 0, NULL },
 	{ "default-terminal", SET_OPTION_STRING, 0, 0, NULL },
+	{ "detach-on-destroy", SET_OPTION_FLAG, 0, 0, NULL },
 	{ "display-panes-colour", SET_OPTION_COLOUR, 0, 0, NULL },
 	{ "display-panes-active-colour", SET_OPTION_COLOUR, 0, 0, NULL },
 	{ "display-panes-time", SET_OPTION_NUMBER, 1, INT_MAX, NULL },

server-fn.c

@@ -24,6 +24,7 @@
 
 #include "tmux.h"
 
+struct session *server_next_session(struct session *);
 void		server_callback_identify(int, short, void *);
 
 void
@@ -358,18 +359,47 @@ server_destroy_session_group(struct session *s)
 	}
 }
 
+struct session *
+server_next_session(struct session *s)
+{
+	struct session *s_loop, *s_out;
+	u_int		i;
+
+	s_out = NULL;
+	for (i = 0; i < ARRAY_LENGTH(&sessions); i++) {
+		s_loop = ARRAY_ITEM(&sessions, i);
+		if (s_loop == s)
+			continue;
+		if (s_out == NULL ||
+		    timercmp(&s_loop->activity_time, &s_out->activity_time, <))
+			s_out = s_loop;
+	}
+	return (s_out);
+}
+
 void
 server_destroy_session(struct session *s)
 {
 	struct client	*c;
+	struct session	*s_new;
 	u_int		 i;
 
+	if (!options_get_number(&s->options, "detach-on-destroy"))
+		s_new = server_next_session(s);
+	else
+		s_new = NULL;
+
 	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
 		c = ARRAY_ITEM(&clients, i);
 		if (c == NULL || c->session != s)
 			continue;
+		if (s_new == NULL) {
 			c->session = NULL;
 			server_write_client(c, MSG_EXIT, NULL, 0);
+		} else {
+			c->session = s_new;
+			server_redraw_client(c);
+		}
 	}
 	recalculate_sizes();
 }

tmux.1

@@ -1557,6 +1557,11 @@ Available window options are listed under
 .Pp
 Available server options are:
 .Bl -tag -width Ds
+.It Ic detach-on-destroy
+If on (the default), the client is detached when the session it is attached to
+is destroyed.
+If off, the client is switched to the most recently active of the remaining
+sessions.
 .It Ic escape-time
 Set the time in milliseconds for which
 .Nm

tmux.c

@@ -341,8 +341,9 @@ main(int argc, char **argv)
 	options_set_string(so, "default-command", "%s", "");
 	options_set_string(so, "default-shell", "%s", getshell());
 	options_set_string(so, "default-terminal", "screen");
-	options_set_number(so, "display-panes-colour", 4);
+	options_set_number(so, "detach-on-destroy", 1);
 	options_set_number(so, "display-panes-active-colour", 1);
+	options_set_number(so, "display-panes-colour", 4);
 	options_set_number(so, "display-panes-time", 1000);
 	options_set_number(so, "display-time", 750);
 	options_set_number(so, "history-limit", 2000);