Add two new values for the destroy-unattached option to destroy sessions

only if they are not members of sessions groups, from Mark Huang, GitHub
issue 3806.

options-table.c

@@ -85,6 +85,9 @@ static const char *options_table_window_size_list[] = {
 static const char *options_table_remain_on_exit_list[] = {
 	"off", "on", "failed", NULL
 };
+static const char *options_table_destroy_unattached_list[] = {
+	"off", "on", "keep-last", "keep-group", NULL
+};
 static const char *options_table_detach_on_destroy_list[] = {
 	"off", "on", "no-detached", "previous", "next", NULL
 };
@@ -484,11 +487,12 @@ const struct options_table_entry options_table[] = {
 	},
 
 	{ .name = "destroy-unattached",
-	  .type = OPTIONS_TABLE_FLAG,
+	  .type = OPTIONS_TABLE_CHOICE,
 	  .scope = OPTIONS_TABLE_SESSION,
+	  .choices = options_table_destroy_unattached_list,
 	  .default_num = 0,
 	  .text = "Whether to destroy sessions when they have no attached "
-		  "clients."
+		  "clients, or keep the last session whether in the group."
 	},
 
 	{ .name = "detach-on-destroy",

proc.c

@@ -92,7 +92,7 @@ proc_event_cb(__unused int fd, short events, void *arg)
 			log_debug("peer %p message %d", peer, imsg.hdr.type);
 
 			if (peer_check_version(peer, &imsg) != 0) {
-				int fd = imsg_get_fd(&imsg);
+				fd = imsg_get_fd(&imsg);
 				if (fd != -1)
 					close(fd);
 				imsg_free(&imsg);

server-fn.c

@@ -454,7 +454,8 @@ server_destroy_session(struct session *s)
 void
 server_check_unattached(void)
 {
-	struct session	*s;
+	struct session		*s;
+	struct session_group	*sg;
 
 	/*
 	 * If any sessions are no longer attached and have destroy-unattached
@@ -463,8 +464,23 @@ server_check_unattached(void)
 	RB_FOREACH(s, sessions, &sessions) {
 		if (s->attached != 0)
 			continue;
-		if (options_get_number (s->options, "destroy-unattached"))
+		switch (options_get_number(s->options, "destroy-unattached")) {
-			session_destroy(s, 1, __func__);
+		case 0: /* off */
+			continue;
+		case 1: /* on */
+			break;
+		case 2: /* keep-last */
+			sg = session_group_contains(s);
+			if (sg == NULL || session_group_count(sg) <= 1)
+				continue;
+			break;
+		case 3: /* keep-group */
+			sg = session_group_contains(s);
+			if (sg != NULL && session_group_count(sg) == 1)
+				continue;
+			break;
+		}
+		session_destroy(s, 1, __func__);
 	}
 }
 

tmux.1

@@ -4023,10 +4023,20 @@ The value is the width and height separated by an
 character.
 The default is 80x24.
 .It Xo Ic destroy-unattached
-.Op Ic on | off
+.Op Ic off | on | keep-last | keep-group
 .Xc
-If enabled and the session is no longer attached to any clients, it is
+If
-destroyed.
+.Ic on ,
+destroy the session after the last client has detached.
+If
+.Ic off
+(the default), leave the session orphaned.
+If
+.Ic keep-last ,
+destroy the session only if it is in a group and has other sessions in that group.
+If
+.Ic keep-group ,
+destroy the session unless it is in a group and is the only session in that group.
 .It Xo Ic detach-on-destroy
 .Op Ic off | on | no-detached | previous | next
 .Xc