Cmd can be passthrough now, too.

Fixes #253.

context.go

@@ -361,6 +361,10 @@ func (c *Context) trace(node *Node) (err error) { // nolint: gocyclo
 		flags = append(flags, group...)
 	}
 
+	if node.Passthrough {
+		c.endParsing()
+	}
+
 	for !c.scan.Peek().IsEOL() {
 		token := c.scan.Peek()
 		switch token.Type {
@@ -901,6 +905,16 @@ func checkEnum(value *Value, target reflect.Value) error {
 	}
 }
 
+func checkPassthroughArg(target reflect.Value) bool {
+	typ := target.Type()
+	switch typ.Kind() {
+	case reflect.Slice:
+		return typ.Elem().Kind() == reflect.String
+	default:
+		return false
+	}
+}
+
 func checkXorDuplicates(paths []*Path) error {
 	for _, path := range paths {
 		seen := map[string]*Flag{}