Only run the unit tests which touch changed code in the ci

[max-models]

Redo of #50

Solves the following issue(s):

Closes #45

Core changes:

There are now four PR workflows that must pass for a feature to be merged:

1. unit
2. models
3. pure Python
4. with clones

Tests are made with and without MPI with --testmon. Testmon data is cached for the next workflow run to use. Cache cannot be altered, thus new cache keys are necessary in every run. The key convention is, for unit tests for example:

key: testmon-unit-${{ github.event.number }}-${{ github.run_number }}
restore-keys: |
    testmon-unit-${{ github.event.number }}-
    testmon-unit-

The event.number is the number of the PR. The run_number refers to the workflow run, thus it increases monotonically. The one that is fetched has a run number one less than the current run, and is thus the most recent.

[spossann]

@max-models what is the status on this one? It would be really nice to have it working to shorten the time of unit tests.

[max-models]

@max-models what is the status on this one? It would be really nice to have it working to shorten the time of unit tests.

I think it already works for the single core unit tests, but not for the MPI tests. I don't have any time to finish it this week, the best option would probably be to do it in two separate PRs.

[spossann]

@max-models could please also review this? Thx!

[max-models]

@max-models could please also review this? Thx!

Of course!

[max-models]

I would approve the PR now, but I can't because I'm the author of the PR. Can you do it?

[max-models]

Nice! I expect this to speed up development by 100x :)