Incremental verifying

[damithc]

Recently we encountered a case where the verifying needs to be done in stages i.e., ask the student do the first step of the task -> verify it -> give feedback -> ask the student to proceed to next step -> ...

Keep in mind that this incremental verification may not be entirely passive. In some cases, the verifier might need to do further scaffolding in the repo before the student can proceed.

e.g., after student merges a branch, the verifier might need to create another branch, to simulate a situation of a team member working in parallel.

Just something to keep in mind when implementing incremental verifying.

[woojiahao]

I was actually trying to implement it with the latest few exercises, but realized that for those, it's not really a strong use case. The existing checks already happen "incrementally" where we verify that task 1 is complete, else we error. Then, we proceed with checks for the remaining tasks, so there was no strong need for checkpoints.

However, I do agree that this might be something we want to support in the future since this might actually be a full workflow. I was thinking that we can trial this with the actual collaborative workflow exercises instead.