cmd/loop: add new keyword argument for amt

In this commit there is a new keyword argument for amt to add an alternative to the positional argument for amt

cmd/loop/loopout.go

@@ -31,24 +31,33 @@ var loopOutCommand = cli.Command{
 				"should be sent to, if let blank the funds " +
 				"will go to lnd's wallet",
 		},
+		cli.Uint64Flag{
+			Name:   "amt",
+			Usage:  "the amount in satoshis to loop out",
+		},
 	},
 	Action: loopOut,
 }
 
 func loopOut(ctx *cli.Context) error {
-	// Show command help if no arguments and flags were provided.
-	if ctx.NArg() < 1 {
-		cli.ShowCommandHelp(ctx, "out")
-		return nil
-	}
-
 	args := ctx.Args()
 
-	amt, err := parseAmt(args[0])
+	var amtStr string
+	if ctx.IsSet("amt") {
+	   amtStr = ctx.String("amt")
+	} else if ctx.NArg() > 0 {
+	   amtStr = args[0]
+	   args = args.Tail()
+	} else {
+	   // Show command help if no arguments and flags were provided.
+	   cli.ShowCommandHelp(ctx, "out")
+	   return nil
+	}
+
+	amt, err := parseAmt(amtStr)
 	if err != nil {
 		return err
 	}
-	args = args.Tail()
 
 	var destAddr string
 	switch {