VMR Code Flow PoC

[premun]

Context

As a result of the design for full code flow (being worked as part of dotnet/arcade#14195), we plan to implement darc commands that would perform the forward and backward flow.
We want to test the logic on local scenarios, utilizing the E2E infra we already have for the current VMR code.

Goals

• We have a new VMR command that will accept either a VMR SHA or a VMR build ID and flow that build into a local folder of a repository based on the code flow configuration.
• We have a new VMR command that will locally flow code from a repo to the VMR.
• We have a set of E2E tests that validate that the flow works for the most common cases:
  • Code flowing between repos and VMR without conflicts
  • Conflicts happening on either side and propagated back

[premun]

The PoC is in this branch - https://github.com/premun/arcade-services/tree/prvysoky/codeflow-poc

[premun]

I have implemented all of the diagrams from the backflow design and they work like expected. The code has many TODOs so far which need to be resolved. But otherwise we have E2E tests verifying all of the flows.

[premun]

This has been completed - we have a basic full code flow implemented with E2E tests verifying the file manipulations.
What is left is to plug this in with BAR and using BAR builds with real assets to move the code.