Add delay flag to prevent hitting rate limits with remote state

Set a default delay of 2s, which is working for remote state with the
google terraform provider

main.go

@@ -2,35 +2,48 @@
 package main
 
 import (
+	"fmt"
 	"github.com/urfave/cli/v2"
 	"log"
 	"os"
 	"reflect"
+	"time"
 )
 
 var (
 	version = "dev"
 )
 
+type config struct {
+	delay time.Duration
+}
+
 func main() {
 	app := &cli.App{
-		Name:      "terraform-state-mover",
-		Usage:     "refactoring Terraform code has never been easier",
-		Authors:   []*cli.Author{{Name: "Maximilian Bode", Email: "maxbode@gmail.com"}},
-		Action:    action,
-		UsageText: "terraform-state-mover [-- <terraform args>]",
-		Version:   version,
+		Name:    "terraform-state-mover",
+		Usage:   "refactoring Terraform code has never been easier",
+		Authors: []*cli.Author{{Name: "Maximilian Bode", Email: "maxbode@gmail.com"}},
+		Action:  action,
+		Flags: []cli.Flag{
+			&cli.DurationFlag{
+				Name: "delay", Aliases: []string{"d"},
+				Usage: "Delay between terraform state mv calls. Helps to avoid rate-limits.",
+				Value: time.Second * 2,
+			},
+		},
+		Version: version,
 	}
 	if err := app.Run(os.Args); err != nil {
 		log.Fatal(err)
 	}
 }
 
-func action(c *cli.Context) error {
+func action(ctx *cli.Context) error {
 	var args []string
 	if len(os.Args) >= 2 && os.Args[1] == "--" {
 		args = os.Args[2:]
 	}
+	cfg := readConfig(ctx)
 
 	changes, err := changes(args)
 	if err != nil {
@@ -53,10 +66,23 @@ func action(c *cli.Context) error {
 		delete(dests, dest)
 	}
 
+	if len(moves) == 0 {
+		fmt.Println("Nothing to do.")
+	}
 	for src, dest := range moves {
 		if err := move(src, dest); err != nil {
 			return err
 		}
 	}
 	return nil
 }
+
+func readConfig(ctx *cli.Context) config {
+	return config{
+		delay: ctx.Duration("delay"),
+	}
+}
+
+func wait(cfg config) {
+	time.Sleep(cfg.delay)
+}