feat(aws-codepipeline): New Pipeline#addStage convenience method.

Added to make creating Stage objects a little more concise.

packages/@aws-cdk/aws-codepipeline/README.md

@@ -11,11 +11,12 @@ const pipeline = new Pipeline(this, 'MyFirstPipeline', {
 Append a Stage to the Pipeline:
 
 ```ts
-const sourceStage = new Stage(this, 'Source', {
-    pipeline,
-});
+const sourceStage = pipeline.addStage('Source');
 ```
 
+You can also instantiate the `Stage` Construct directly,
+which will add it to the Pipeline provided in its construction properties.
+
 Add an Action to a Stage:
 
 ```ts

packages/@aws-cdk/aws-codepipeline/lib/pipeline.ts

@@ -121,6 +121,19 @@ export class Pipeline extends cdk.Construct implements events.IEventRuleTarget {
         }));
     }
 
+    /**
+     * Convenience method for creating a new {@link Stage},
+     * and adding it to this Pipeline.
+     *
+     * @param name the name of the newly created Stage
+     * @returns the newly created Stage
+     */
+    public addStage(name: string): Stage {
+        return new Stage(this, name, {
+            pipeline: this,
+        });
+    }
+
     /**
      * Adds a statement to the pipeline role.
      */

packages/@aws-cdk/aws-codepipeline/test/integ.pipeline-code-commit.ts

@@ -10,7 +10,7 @@ const repo = new codecommit.Repository(stack, 'MyRepo', { repositoryName: 'my-re
 
 const pipeline = new codepipeline.Pipeline(stack, 'Pipeline');
 
-const sourceStage = new codepipeline.Stage(pipeline, 'source', { pipeline });
+const sourceStage = pipeline.addStage('source');
 repo.addToPipeline(sourceStage, 'source', {
     artifactName: 'SourceArtifact',
 });

packages/@aws-cdk/aws-codepipeline/test/test.stages.ts

@@ -0,0 +1,24 @@
+import { expect, haveResource } from '@aws-cdk/assert';
+import cdk = require('@aws-cdk/cdk');
+import { Test } from 'nodeunit';
+import codepipeline = require('../lib');
+
+// tslint:disable:object-literal-key-quotes
+
+export = {
+    'Pipeline Stages': {
+        'can also be created by using the Pipeline#addStage method'(test: Test) {
+            const stack = new cdk.Stack();
+            const pipeline = new codepipeline.Pipeline(stack, 'Pipeline');
+            pipeline.addStage('Stage');
+
+            expect(stack, true).to(haveResource('AWS::CodePipeline::Pipeline', {
+                "Stages": [
+                    { "Name": "Stage" },
+                ],
+            }));
+
+            test.done();
+        },
+    },
+};