Add ClassifyFiles.ql

ql/src/filters/ClassifyFiles.ql

@@ -0,0 +1,20 @@
+/**
+ * @name Classify files
+ * @description This query produces a list of all files in a database
+ *              that are classified as generated code or test code.
+ *
+ *              Used by LGTM.
+ * @kind file-classifier
+ * @id rb/file-classifier
+ */
+
+import ruby
+import codeql.ruby.filters.GeneratedCode
+
+predicate classify(File f, string category) {
+  f instanceof GeneratedCodeFile and category = "generated"
+}
+
+from File f, string category
+where classify(f, category)
+select f, category