cmd/utils: customize cli.HelpPrinter to fix alignment (#19956)

This copies cli.printHelp but changes minwidth to 38. Custom flag
code is improved to print the default value using cli.FlagStringer like
all built-in flags do.

cmd/utils/flags.go

@@ -21,12 +21,15 @@ import (
 	"crypto/ecdsa"
 	"errors"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"math/big"
 	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
+	"text/tabwriter"
+	"text/template"
 	"time"
 
 	"github.com/ethereum/go-ethereum/accounts"
@@ -90,8 +93,8 @@ GLOBAL OPTIONS:
    {{range .Flags}}{{.}}
    {{end}}{{end}}
 `
-
 	cli.CommandHelpTemplate = CommandHelpTemplate
+	cli.HelpPrinter = printHelp
 }
 
 // NewApp creates an app with sane defaults.
@@ -105,6 +108,17 @@ func NewApp(gitCommit, gitDate, usage string) *cli.App {
 	return app
 }
 
+func printHelp(out io.Writer, templ string, data interface{}) {
+	funcMap := template.FuncMap{"join": strings.Join}
+	t := template.Must(template.New("help").Funcs(funcMap).Parse(templ))
+	w := tabwriter.NewWriter(out, 38, 8, 2, ' ', 0)
+	err := t.Execute(w, data)
+	if err != nil {
+		panic(err)
+	}
+	w.Flush()
+}
+
 // These are all the command line flags we support.
 // If you add to this list, please remember to include the
 // flag in the appropriate command definition.
@@ -117,7 +131,7 @@ var (
 	DataDirFlag = DirectoryFlag{
 		Name:  "datadir",
 		Usage: "Data directory for the databases and keystore",
-		Value: DirectoryString{node.DefaultDataDir()},
+		Value: DirectoryString(node.DefaultDataDir()),
 	}
 	AncientFlag = DirectoryFlag{
 		Name:  "datadir.ancient",
@@ -168,7 +182,7 @@ var (
 	DocRootFlag = DirectoryFlag{
 		Name:  "docroot",
 		Usage: "Document Root for HTTPClient file scheme",
-		Value: DirectoryString{homeDir()},
+		Value: DirectoryString(homeDir()),
 	}
 	ExitWhenSyncedFlag = cli.BoolFlag{
 		Name:  "exitwhensynced",
@@ -291,8 +305,8 @@ var (
 	}
 	EthashDatasetDirFlag = DirectoryFlag{
 		Name:  "ethash.dagdir",
-		Usage: "Directory to store the ethash mining DAGs (default = inside home folder)",
-		Value: DirectoryString{eth.DefaultConfig.Ethash.DatasetDir},
+		Usage: "Directory to store the ethash mining DAGs",
+		Value: DirectoryString(eth.DefaultConfig.Ethash.DatasetDir),
 	}
 	EthashDatasetsInMemoryFlag = cli.IntFlag{
 		Name:  "ethash.dagsinmem",