Add HideHelpCommand

While `HideHelp` hides both `help` command and `--help` flag, `HideHelpCommand`
only hides `help` command and leave `--help` flag as-is.

The behavior of `HideHelp` is untouched in this commit.

Fix #523
Replace #636

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

app.go

@@ -43,8 +43,10 @@ type App struct {
 	Flags []Flag
 	// Boolean to enable bash completion commands
 	EnableBashCompletion bool
-	// Boolean to hide built-in help command
+	// Boolean to hide built-in help command and help flag
 	HideHelp bool
+	// Boolean to hide built-in help command but keep help flag
+	HideHelpCommand bool
 	// Boolean to hide built-in version flag and the VERSION section of help
 	HideVersion bool
 	// categories contains the categorized commands and is populated on app startup
@@ -170,7 +172,9 @@ func (a *App) Setup() {
 	a.Commands = newCommands
 
 	if a.Command(helpCommand.Name) == nil && !a.HideHelp {
-		a.appendCommand(helpCommand)
+		if !a.HideHelpCommand {
+			a.appendCommand(helpCommand)
+		}
 
 		if HelpFlag != nil {
 			a.appendFlag(HelpFlag)
@@ -333,7 +337,9 @@ func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 	// append help to commands
 	if len(a.Commands) > 0 {
 		if a.Command(helpCommand.Name) == nil && !a.HideHelp {
-			a.appendCommand(helpCommand)
+			if !a.HideHelpCommand {
+				a.appendCommand(helpCommand)
+			}
 
 			if HelpFlag != nil {
 				a.appendFlag(HelpFlag)

app_test.go

@@ -2152,3 +2152,40 @@ func newTestApp() *App {
 	a.Writer = ioutil.Discard
 	return a
 }
+
+func TestHideHelpCommand(t *testing.T) {
+	app := &App{
+		HideHelpCommand: true,
+		Writer:          ioutil.Discard,
+	}
+
+	err := app.Run([]string{"foo", "help"})
+	if err == nil {
+		t.Fatalf("expected a non-nil error")
+	}
+	if !strings.Contains(err.Error(), "No help topic for 'help'") {
+		t.Errorf("Run returned unexpected error: %v", err)
+	}
+
+	err = app.Run([]string{"foo", "--help"})
+	if err != nil {
+		t.Errorf("Run returned unexpected error: %v", err)
+	}
+}
+
+func TestHideHelpCommandFalse(t *testing.T) {
+	app := &App{
+		HideHelpCommand: false,
+		Writer:          ioutil.Discard,
+	}
+
+	err := app.Run([]string{"foo", "help"})
+	if err != nil {
+		t.Errorf("Run returned unexpected error: %v", err)
+	}
+
+	err = app.Run([]string{"foo", "--help"})
+	if err != nil {
+		t.Errorf("Run returned unexpected error: %v", err)
+	}
+}

command.go

@@ -41,8 +41,10 @@ type Command struct {
 	Flags []Flag
 	// Treat all flags as normal arguments if true
 	SkipFlagParsing bool
-	// Boolean to hide built-in help command
+	// Boolean to hide built-in help command and help flag
 	HideHelp bool
+	// Boolean to hide built-in help command but keep help flag
+	HideHelpCommand bool
 	// Boolean to hide this command from help or completion
 	Hidden bool
 	// Boolean to enable short-option handling so user can combine several
@@ -236,6 +238,7 @@ func (c *Command) startApp(ctx *Context) error {
 	app.Commands = c.Subcommands
 	app.Flags = c.Flags
 	app.HideHelp = c.HideHelp
+	app.HideHelpCommand = c.HideHelpCommand
 
 	app.Version = ctx.App.Version
 	app.HideVersion = ctx.App.HideVersion

flag.go

@@ -36,7 +36,7 @@ var VersionFlag Flag = &BoolFlag{
 
 // HelpFlag prints the help for all commands and subcommands.
 // Set to nil to disable the flag.  The subcommand
-// will still be added unless HideHelp is set to true.
+// will still be added unless HideHelp or HideHelpCommand is set to true.
 var HelpFlag Flag = &BoolFlag{
 	Name:    "help",
 	Aliases: []string{"h"},