Cache GMT remote data as artifacts on Github

[weiji14]

Description of proposed changes

Use GMT on macOS to download the GMT remote files from the GMT data server, and then upload them as artifacts on Github.

Separates the 'cache' task from our Tests CI. Meaning we can update our cache independently of our Continuous Integration tests, allowing the cache to be updated every Sunday for example without needing to manually trigger it with a PR.

References:

• https://docs.github.com/en/actions/configuring-and-managing-workflows/persisting-workflow-data-using-artifacts
• https://github.com/actions/upload-artifact
• https://github.com/dawidd6/action-download-artifact
• https://github.com/actions/download-artifact
• https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#onschedule

Fixes#523, Closes#527

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If adding new functionality, add an example to docstrings or tutorials.

[seisman]

Is the path correct? Downloading artifacts is fast, but it may not be placed in the correct directories. GMT still tries to download all files during testing.

[weiji14]

Hmm, it looks like it's unzipped to the right location (e.g. ~/.gmt/server/earth/earth_relief/earth_relief_01d_g.grd), and that's what wget was doing before?? Maybe we should use $HOME or something?

[seisman]

I think you can add a step listing all files in the ~/.gmt directory after downloading the artifacts.

[weiji14]

Hmm, $HOME doesn't work either. Then I'm not sure where the action is actually unzipping the files to!

[seisman]

I've some tests to do, and will make changes to this branch.

[weiji14]

Ok, go for it 👍

[weiji14]

I see that a ~ folder is created 🤦. How about trying ./.gmt, since the action uses ./ as the default, see https://github.com/dawidd6/action-download-artifact/blob/2f29da2bb95f5580767170955fca0cf48714d48b/action.yml#L31. Also, we should use ls -alh to see hidden dot files.

Edit: What am I saying, I should just use .gmt!

[seisman]

I saw the .gmt directory in the root directory. At least we can download the artifact, and then move it to ~/.

[weiji14]

Yes, that's one way of doing it.