Allow hiding of help flag without hiding help subcommand

By utilizing struct zero value

app.go

@@ -70,7 +70,9 @@ func (a *App) Run(arguments []string) error {
 	// append help to commands
 	if a.Command(helpCommand.Name) == nil && !a.HideHelp {
 		a.Commands = append(a.Commands, helpCommand)
-		a.appendFlag(HelpFlag)
+		if (HelpFlag != BoolFlag{}) {
+			a.appendFlag(HelpFlag)
+		}
 	}
 
 	//append version/help flags
@@ -150,7 +152,9 @@ func (a *App) RunAsSubcommand(ctx *Context) error {
 	if len(a.Commands) > 0 {
 		if a.Command(helpCommand.Name) == nil && !a.HideHelp {
 			a.Commands = append(a.Commands, helpCommand)
-			a.appendFlag(HelpFlag)
+			if (HelpFlag != BoolFlag{}) {
+				a.appendFlag(HelpFlag)
+			}
 		}
 	}
 

app_test.go

@@ -1,6 +1,7 @@
 package cli_test
 
 import (
+	"flag"
 	"fmt"
 	"os"
 	"testing"
@@ -331,6 +332,22 @@ func TestApp_BeforeFunc(t *testing.T) {
 
 }
 
+func TestAppNoHelpFlag(t *testing.T) {
+	oldFlag := cli.HelpFlag
+	defer func() {
+		cli.HelpFlag = oldFlag
+	}()
+
+	cli.HelpFlag = cli.BoolFlag{}
+
+	app := cli.NewApp()
+	err := app.Run([]string{"test", "-h"})
+
+	if err != flag.ErrHelp {
+		t.Errorf("expected error about missing help flag, but got: %s (%T)", err, err)
+	}
+}
+
 func TestAppHelpPrinter(t *testing.T) {
 	oldPrinter := cli.HelpPrinter
 	defer func() {

command.go

@@ -40,7 +40,7 @@ func (c Command) Run(ctx *Context) error {
 		return c.startApp(ctx)
 	}
 
-	if !c.HideHelp {
+	if !c.HideHelp && (HelpFlag != BoolFlag{}) {
 		// append help to flags
 		c.Flags = append(
 			c.Flags,

flag.go

@@ -21,6 +21,8 @@ var VersionFlag = BoolFlag{
 }
 
 // This flag prints the help for all commands and subcommands
+// Set to the zero value (BoolFlag{}) to disable flag -- keeps subcommand
+// unless HideHelp is set to true)
 var HelpFlag = BoolFlag{
 	Name:  "help, h",
 	Usage: "show help",