passing the no-more-options string "--" twice or more should pass the…

… second and subsequent ones through as positionals

parse.go

@@ -615,7 +615,7 @@ func (p *Parser) process(args []string) error {
 	// must use explicit for loop, not range, because we manipulate i inside the loop
 	for i := 0; i < len(args); i++ {
 		arg := args[i]
-		if arg == "--" {
+		if arg == "--" && !allpositional {
 			allpositional = true
 			continue
 		}

parse_test.go

@@ -609,6 +609,15 @@ func TestNoMoreOptionsBeforeHelp(t *testing.T) {
 	assert.NotEqual(t, ErrHelp, err)
 }
 
+func TestNoMoreOptionsTwice(t *testing.T) {
+	var args struct {
+		X []string `arg:"positional"`
+	}
+	err := parse("-- --", &args)
+	require.NoError(t, err)
+	assert.Equal(t, []string{"--"}, args.X)
+}
+
 func TestHelpFlag(t *testing.T) {
 	var args struct {
 		Foo string