fix[file-header]: fix enforce-trailing-newline option

src/rules/fileHeaderRule.ts

@@ -244,9 +244,7 @@ export class Rule extends Lint.Rules.AbstractRule {
         );
 
         const NEW_LINE_FOLLOWING_HEADER = /^.*((\r)?\n){2,}$/gm;
-        return (
-            entireComment !== undefined && NEW_LINE_FOLLOWING_HEADER.test(entireComment) !== null
-        );
+        return entireComment !== undefined && !NEW_LINE_FOLLOWING_HEADER.test(entireComment);
     }
 
     private getFileHeaderText(

test/rules/file-header/good-newline/test.ts.lint

@@ -0,0 +1,3 @@
+/* Copyright 2019 */
+
+class Foo {}

test/rules/file-header/good-newline/tslint.json

@@ -0,0 +1,10 @@
+{
+    "rules": {
+        "file-header": [
+            true,
+            "Copyright \\d{4}",
+            "Copyright 2019",
+            "enforce-trailing-newline"
+        ]
+    }
+}