Refactor extra watch options regex to react-dev-utils (#3362)

* extra watch options regex to react-dev-utils

* fix regex

* add test

* fix eslint error

* include react-dev-utils test in CI script

* attempt to fix import error

* attempt to fix error on CI

* Update .eslintrc

packages/react-dev-utils/__tests__/.eslintrc

@@ -0,0 +1,5 @@
+{
+  "env": {
+    "jest": true
+  }
+}

packages/react-dev-utils/__tests__/ignoredFiles.test.js

@@ -0,0 +1,55 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+'use strict';
+
+const ignoredFiles = require('../ignoredFiles');
+
+describe('ignore watch files regex', () => {
+  it('normal file', () => {
+    const appSrc = '/root/src/';
+    const isIgnored = ignoredFiles(appSrc).test('/foo');
+    const isIgnoredInSrc = ignoredFiles(appSrc).test('/root/src/foo');
+
+    expect(isIgnored).toBe(false);
+    expect(isIgnoredInSrc).toBe(false);
+  });
+
+  it('node modules', () => {
+    const appSrc = '/root/src/';
+    const isIgnored = ignoredFiles(appSrc).test('/root/node_modules/foo');
+
+    expect(isIgnored).toBe(true);
+  });
+
+  it('node modules inside source directory', () => {
+    const appSrc = '/root/src/';
+    const isIgnored = ignoredFiles(appSrc).test('/root/src/node_modules/foo');
+    const isIgnoredMoreThanOneLevel = ignoredFiles(appSrc).test(
+      '/root/src/bar/node_modules/foo'
+    );
+
+    expect(isIgnored).toBe(false);
+    expect(isIgnoredMoreThanOneLevel).toBe(false);
+  });
+
+  it('path contains source directory', () => {
+    const appSrc = '/root/src/';
+    const isIgnored = ignoredFiles(appSrc).test(
+      '/bar/root/src/node_modules/foo'
+    );
+
+    expect(isIgnored).toBe(true);
+  });
+
+  it('path starts with source directory', () => {
+    const appSrc = '/root/src/';
+    const isIgnored = ignoredFiles(appSrc).test('/root/src2/node_modules/foo');
+
+    expect(isIgnored).toBe(true);
+  });
+});