Pipeline: Create integration tests for `knative/serving` with PipelineRun + TaskRun

[bobcatfish]

Expected Behavior

In github.com/knative/serving, a Configuration (see overview) can contain a Build, which can be used to build the image which will be used in the Revision.

Thanks to duck typing (viewable by members of knative-dev@), it should be possible to use a PipelineRun or a TaskRun instead.

We should have e2e tests (maybe even confromance tests?) inside knative/serving which verify that Build can be swapped out for a TaskRun or a PipelineRun.

Actual Behavior

While this theoretically should work, we haven't tried it and there is nothing to ensure this keeps working over time.

Steps to Reproduce the Problem

The test should:

1. Create a Configuration where the spec.build contains a TaskRun definition that uses a Task which builds the image which the Revision will use.
2. Deploy the Configuration
3. Verify that the image was built and deployed

Repeat the same for a PipelineRun.

Additional Info

Part of #147

[nader-ziada]

@bobcatfish I think we need to have a release of pipeline first before we can a release.yaml in serving and try using it, wdyt?

[bobcatfish]

yeah that makes sense @pivotal-nader-ziada - the issue blocking this one then is #219

[bobcatfish]

After discussing with @pivotal-nader-ziada @shashwathi @ImJasonH we think we can go forward for now by vendoring Pipelines at an arbitrary nightly release commit (maybe take a look at how serving currently vendors Build as well).

[vdemeester]

/assign

[tejal29]

@vdemeester are you actively working on this one? I am looking to jump in on 0.4 release milestone issues.

[vdemeester]

@tejal29 I started working on it yes, but digging into knative/serving, turns out knative/build is used there only for the API types, the test are using a fake building CRD (to be decoupled from the build component)

cc @mattmoor to tell me I'm wrong (or hopefully not :angel:)