Add api command

cmd/sing-box/cmd_api_group.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"github.com/sagernet/sing-box/daemon"
+
+	"github.com/spf13/cobra"
+	"google.golang.org/protobuf/types/known/emptypb"
+)
+
+var commandAPIGroup = &cobra.Command{
+	Use:   "group",
+	Short: "Manage outbound groups",
+}
+
+func init() {
+	commandAPIRoot.AddCommand(commandAPIGroup)
+}
+
+func fetchGroups(client daemon.StartedServiceClient) ([]*daemon.Group, error) {
+	stream, err := client.SubscribeGroups(globalCtx, &emptypb.Empty{})
+	if err != nil {
+		return nil, err
+	}
+	groups, err := stream.Recv()
+	if err != nil {
+		return nil, err
+	}
+	return groups.GetGroup(), nil
+}