add simple description in command

cmd/listen.go

@@ -23,6 +23,13 @@ import (
 var listenCmd = &cobra.Command{
 	Use:   "listen",
 	Short: "Start webhook listener",
+	Long: `Start webhook listener
+
+Webhook mode utilized Forgejo's webhook to update pages. You have to setup webhook
+in Forgejo's settings page to point to this server. When a push event is received,
+this server will pull the repository and update the pages. How the pages are served
+is up to you, eg. Nginx, Apache, or even a simple Go server.
+`,
 	Run: func(cmd *cobra.Command, args []string) {
 		viper.BindPFlags(cmd.Flags())
 		// check flags

cmd/serve.go

@@ -22,6 +22,12 @@ import (
 var serveCmd = &cobra.Command{
 	Use:   "serve",
 	Short: "Start the static page server.",
+	Long: `Start the static page server.
+
+Serve mode will start a HTTP server to serve static pages. It just forward requests
+to Forgejo server. This is useful when there is not much viewers, or you have other
+cache/protection layer like Cloudflare in front of the server.
+`,
 	Run: func(cmd *cobra.Command, args []string) {
 		viper.BindPFlags(cmd.Flags())
 		// check flags