add "cluster compare" command and add 1st check (unsync indices) (#2)

cmd/root.go

@@ -76,11 +76,12 @@ func Main() int {
 			Search(conf),
 			Index(conf),
 			Snapshot(conf),
+			Cluster(conf),
 		},
 
 		Before: func(ctx context.Context, cmd *cli.Command) (context.Context, error) {
 			if err := conf.Init(); err != nil {
-				Finish(err)
+				return nil, err
 			}
 
 			log.Init(conf)