Add CI

[clelange]

• Add small ROOT file with histograms that can be used for plotting
• Create script to use this ROOT file to create plots from
• Use this script in CI (GitLab CI or GitHub Actions or both)

[andrzejnovak]

Better to depend on skhep_data for test instead of a committed ROOT file eghttps://github.com/scikit-hep/mplhep/blob/master/tests/test_inputs.py#L41

Can also just create TH1s on the fly with uproot ROOT :).

[clelange]

Thanks for the pointer, but I'm not sure, it adds a dependency that might make it more difficult for people to contribute. Would surely need "contributing" docs.

[andrzejnovak]

I'm happy to help with image comparison tests in CI also. I've set them up for mplhep, but perhaps we set these up after we settle all the style tweaks.

[oglez]

Hello, I was thinking on working on this for the GitHub version of cmsstyle, but mostly focusing on checking the validity of the code (and mostlyfor me to be sure I did not miss anything while checking before requiring a PR). e.g. to check it actually compiles on the python versions we support.
My plan is to start running these basic checks and the expand. I'll run the thing for sure on "push" as it is what I need :) but glad to start looking into what can be done and when to run the workflows (also when opening a PR? Any other?). Glad to get your input on this!

[clelange]

Great! I think the first step would be to have a small file as listed at #9 (comment) to just run the plot scripts and store them as artifacts.

[oglez]

I think you overestimate my capabilities... I am going to start checking the code I push compile in python and in C++... but yes, next step is about the plot scripts :) Thanks!