feat(dev-infra): create a wizard for building commit messages (#38457)

Creates a wizard to walk through creating a commit message in the correct
template for commit messages in Angular repositories.

PR Close #38457

dev-infra/commit-message/builder.spec.ts

@@ -0,0 +1,46 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import * as config from '../utils/config';
+import * as console from '../utils/console';
+
+import {buildCommitMessage} from './builder';
+
+
+describe('commit message building:', () => {
+  beforeEach(() => {
+    // stub logging calls to prevent noise in test log
+    spyOn(console, 'info').and.stub();
+    // provide a configuration for DevInfra when loaded
+    spyOn(config, 'getConfig').and.returnValue({
+      commitMessage: {
+        scopes: ['core'],
+      }
+    } as any);
+  });
+
+  it('creates a commit message with a scope', async () => {
+    buildPromptResponseSpies('fix', 'core', 'This is a summary');
+
+    expect(await buildCommitMessage()).toMatch(/^fix\(core\): This is a summary/);
+  });
+
+  it('creates a commit message without a scope', async () => {
+    buildPromptResponseSpies('build', false, 'This is a summary');
+
+    expect(await buildCommitMessage()).toMatch(/^build: This is a summary/);
+  });
+});
+
+
+/** Create spies to return the mocked selections from prompts. */
+function buildPromptResponseSpies(type: string, scope: string|false, summary: string) {
+  spyOn(console, 'promptAutocomplete')
+      .and.returnValues(Promise.resolve(type), Promise.resolve(scope));
+  spyOn(console, 'promptInput').and.returnValue(Promise.resolve(summary));
+}