made asc sorting optional and added regression tests

regression_test.go

@@ -0,0 +1,20 @@
+package filter
+
+import "testing"
+
+func TestRegression(t *testing.T) {
+	data := []string{
+		"sort::asc",
+		"Int.:",
+		"String.:",
+		"sort::desc",
+		".:",
+		"sort:.0:asc",
+	}
+	for _, v := range data {
+		_, err := NewQuery(v)
+		if err == nil {
+			t.Errorf("regression: '%s'", v)
+		}
+	}
+}