Support local source code in Shipwright

[qu1queee]

Idea:

Provide support for local source code. But adding here some key points on adopting this feature. EP for feedback.

Context

• IBM folks demo this back in February 2021 @xiujuan95 @mattcui
• Tekton currently does not support this feature.

Requirements

• The implementation to make this work will rely heavily in Shipwright/CLI.
• For this repository(Shipwright/Build) we need to find the right way to signalise to our controllers, the desire of using local source code from users. API changes and code changes when creating a TaskRun are required, in order to make this functional.

Implementation details

• As previously mentioned, we would like to propose an approach where we abuse of the usage of container registries ( you need one to build an image, you probably have one if you are running in k8s ), so that the local source code is pushed into a bundle image that self-extracts on runtime.
• The above is just one approach of many, CLI should be generic enough to extend to further approaches, like relying on s3 to store code or other ways of storing.

Examples

• @mattcui @xiujuan95 demo this repo https://github.com/mattcui/s2i-local.
• @qu1queee have a prototype with shp, see:
  • Changes in Shipwright/Build, see branch
  • Changes in Shipwright/CLI, see branch
    Note: The changes in CLI include a pinned module, please modify this to your local one.

[adambkaplan]

Adding this to the v0.6.0 milestone because this is a feature we would like to have soon. Getting agreement in the enhancement proposal (merged and marked "implementable") is a prerequisite to completing this feature.