cmd: migrate to urfave/cli/v2 (#24751)

This change updates our urfave/cli dependency to the v2 branch of the library.
There are some Go API changes in cli v2:

- Flag values can now be accessed using the methods ctx.Bool,
  ctx.Int, ctx.String, ... regardless of whether the flag is 'local' or
  'global'.

- v2 has built-in support for flag categories. Our home-grown category
  system is removed and the categories of flags are assigned as part of
  the flag definition.

For users, there is only one observable difference with cli v2: flags must now
strictly appear before regular arguments. For example, the following command is
now invalid:

   geth account import mykey.json --password file.txt

Instead, the command must be invoked as follows:

   geth account import --password file.txt mykey.json

cmd/p2psim/main.go

@@ -46,71 +46,77 @@ import (
 	"text/tabwriter"
 
 	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/internal/flags"
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/ethereum/go-ethereum/p2p/simulations"
 	"github.com/ethereum/go-ethereum/p2p/simulations/adapters"
 	"github.com/ethereum/go-ethereum/rpc"
-	"gopkg.in/urfave/cli.v1"
+	"github.com/urfave/cli/v2"
 )
 
 var client *simulations.Client
 
 var (
 	// global command flags
-	apiFlag = cli.StringFlag{
-		Name:   "api",
-		Value:  "http://localhost:8888",
-		Usage:  "simulation API URL",
-		EnvVar: "P2PSIM_API_URL",
+	apiFlag = &cli.StringFlag{
+		Name:    "api",
+		Value:   "http://localhost:8888",
+		Usage:   "simulation API URL",
+		EnvVars: []string{"P2PSIM_API_URL"},
 	}
 
 	// events subcommand flags
-	currentFlag = cli.BoolFlag{
+	currentFlag = &cli.BoolFlag{
 		Name:  "current",
 		Usage: "get existing nodes and conns first",
 	}
-	filterFlag = cli.StringFlag{
+	filterFlag = &cli.StringFlag{
 		Name:  "filter",
 		Value: "",
 		Usage: "message filter",
 	}
 
 	// node create subcommand flags
-	nameFlag = cli.StringFlag{
+	nameFlag = &cli.StringFlag{
 		Name:  "name",
 		Value: "",
 		Usage: "node name",
 	}
-	servicesFlag = cli.StringFlag{
+	servicesFlag = &cli.StringFlag{
 		Name:  "services",
 		Value: "",
 		Usage: "node services (comma separated)",
 	}
-	keyFlag = cli.StringFlag{
+	keyFlag = &cli.StringFlag{
 		Name:  "key",
 		Value: "",
 		Usage: "node private key (hex encoded)",
 	}
 
 	// node rpc subcommand flags
-	subscribeFlag = cli.BoolFlag{
+	subscribeFlag = &cli.BoolFlag{
 		Name:  "subscribe",
 		Usage: "method is a subscription",
 	}
 )
 
+var (
+	// Git information set by linker when building with ci.go.
+	gitCommit string
+	gitDate   string
+)
+
 func main() {
-	app := cli.NewApp()
-	app.Usage = "devp2p simulation command-line client"
+	app := flags.NewApp(gitCommit, gitDate, "devp2p simulation command-line client")
 	app.Flags = []cli.Flag{
 		apiFlag,
 	}
 	app.Before = func(ctx *cli.Context) error {
-		client = simulations.NewClient(ctx.GlobalString(apiFlag.Name))
+		client = simulations.NewClient(ctx.String(apiFlag.Name))
 		return nil
 	}
-	app.Commands = []cli.Command{
+	app.Commands = []*cli.Command{
 		{
 			Name:   "show",
 			Usage:  "show network information",
@@ -139,7 +145,7 @@ func main() {
 			Name:   "node",
 			Usage:  "manage simulation nodes",
 			Action: listNodes,
-			Subcommands: []cli.Command{
+			Subcommands: []*cli.Command{
 				{
 					Name:   "list",
 					Usage:  "list nodes",
@@ -204,7 +210,7 @@ func main() {
 }
 
 func showNetwork(ctx *cli.Context) error {
-	if len(ctx.Args()) != 0 {
+	if ctx.NArg() != 0 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
 	network, err := client.GetNetwork()
@@ -219,7 +225,7 @@ func showNetwork(ctx *cli.Context) error {
 }
 
 func streamNetwork(ctx *cli.Context) error {
-	if len(ctx.Args()) != 0 {
+	if ctx.NArg() != 0 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
 	events := make(chan *simulations.Event)
@@ -245,7 +251,7 @@ func streamNetwork(ctx *cli.Context) error {
 }
 
 func createSnapshot(ctx *cli.Context) error {
-	if len(ctx.Args()) != 0 {
+	if ctx.NArg() != 0 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
 	snap, err := client.CreateSnapshot()
@@ -256,7 +262,7 @@ func createSnapshot(ctx *cli.Context) error {
 }
 
 func loadSnapshot(ctx *cli.Context) error {
-	if len(ctx.Args()) != 0 {
+	if ctx.NArg() != 0 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
 	snap := &simulations.Snapshot{}
@@ -267,7 +273,7 @@ func loadSnapshot(ctx *cli.Context) error {
 }
 
 func listNodes(ctx *cli.Context) error {
-	if len(ctx.Args()) != 0 {
+	if ctx.NArg() != 0 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
 	nodes, err := client.GetNodes()
@@ -292,7 +298,7 @@ func protocolList(node *p2p.NodeInfo) []string {
 }
 
 func createNode(ctx *cli.Context) error {
-	if len(ctx.Args()) != 0 {
+	if ctx.NArg() != 0 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
 	config := adapters.RandomNodeConfig()
@@ -317,11 +323,10 @@ func createNode(ctx *cli.Context) error {
 }
 
 func showNode(ctx *cli.Context) error {
-	args := ctx.Args()
-	if len(args) != 1 {
+	if ctx.NArg() != 1 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
-	nodeName := args[0]
+	nodeName := ctx.Args().First()
 	node, err := client.GetNode(nodeName)
 	if err != nil {
 		return err
@@ -342,11 +347,10 @@ func showNode(ctx *cli.Context) error {
 }
 
 func startNode(ctx *cli.Context) error {
-	args := ctx.Args()
-	if len(args) != 1 {
+	if ctx.NArg() != 1 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
-	nodeName := args[0]
+	nodeName := ctx.Args().First()
 	if err := client.StartNode(nodeName); err != nil {
 		return err
 	}
@@ -355,11 +359,10 @@ func startNode(ctx *cli.Context) error {
 }
 
 func stopNode(ctx *cli.Context) error {
-	args := ctx.Args()
-	if len(args) != 1 {
+	if ctx.NArg() != 1 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
-	nodeName := args[0]
+	nodeName := ctx.Args().First()
 	if err := client.StopNode(nodeName); err != nil {
 		return err
 	}
@@ -368,12 +371,12 @@ func stopNode(ctx *cli.Context) error {
 }
 
 func connectNode(ctx *cli.Context) error {
-	args := ctx.Args()
-	if len(args) != 2 {
+	if ctx.NArg() != 2 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
-	nodeName := args[0]
-	peerName := args[1]
+	args := ctx.Args()
+	nodeName := args.Get(0)
+	peerName := args.Get(1)
 	if err := client.ConnectNode(nodeName, peerName); err != nil {
 		return err
 	}
@@ -383,11 +386,11 @@ func connectNode(ctx *cli.Context) error {
 
 func disconnectNode(ctx *cli.Context) error {
 	args := ctx.Args()
-	if len(args) != 2 {
+	if args.Len() != 2 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
-	nodeName := args[0]
-	peerName := args[1]
+	nodeName := args.Get(0)
+	peerName := args.Get(1)
 	if err := client.DisconnectNode(nodeName, peerName); err != nil {
 		return err
 	}
@@ -397,21 +400,21 @@ func disconnectNode(ctx *cli.Context) error {
 
 func rpcNode(ctx *cli.Context) error {
 	args := ctx.Args()
-	if len(args) < 2 {
+	if args.Len() < 2 {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
-	nodeName := args[0]
-	method := args[1]
+	nodeName := args.Get(0)
+	method := args.Get(1)
 	rpcClient, err := client.RPCClient(context.Background(), nodeName)
 	if err != nil {
 		return err
 	}
 	if ctx.Bool(subscribeFlag.Name) {
-		return rpcSubscribe(rpcClient, ctx.App.Writer, method, args[3:]...)
+		return rpcSubscribe(rpcClient, ctx.App.Writer, method, args.Slice()[3:]...)
 	}
 	var result interface{}
-	params := make([]interface{}, len(args[3:]))
-	for i, v := range args[3:] {
+	params := make([]interface{}, len(args.Slice()[3:]))
+	for i, v := range args.Slice()[3:] {
 		params[i] = v
 	}
 	if err := rpcClient.Call(&result, method, params...); err != nil {