Add <command> to help when a sub-command is required.

_examples/shell/main.go

@@ -13,7 +13,7 @@ var CLI struct {
 	Debug bool `help:"Debug mode."`
 
 	Rm struct {
-		User      string `help:"Run as user." short:"u"`
+		User      string `help:"Run as user." short:"u" default:"default"`
 		Force     bool   `help:"Force removal." short:"f"`
 		Recursive bool   `help:"Recursively remove files." short:"r"`
 

help_test.go

@@ -50,7 +50,7 @@ func TestHelp(t *testing.T) {
 		})
 		require.True(t, exited)
 		t.Log(w.String())
-		require.Equal(t, `usage: test-app --required
+		require.Equal(t, `usage: test-app --required <command>
 
 A test app.
 

model.go

@@ -89,6 +89,8 @@ func (n *Node) Summary() string {
 	}
 	if len(args) != 0 {
 		summary += " " + strings.Join(args, " ")
+	} else if len(n.Children) > 0 {
+		summary += " <command>"
 	}
 	return summary
 }