CI: Upgrade "actions/(checkout|cache)" to version 2

[ShaharNaveh]

According to the change log of both "checkout" and "cache" this should increase performance.

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Fell free to close this PR if this was already discussed, I haven't saw any discussion about this topic.

[fangchenli]

To get all the tags, you need

    - uses: actions/checkout@v2
      with:
        fetch-depth: 0

[datapythonista]

@ShaharNaveh do you have time to have a look at the comment and leave the CI green?

[ShaharNaveh]

@ShaharNaveh do you have time to have a look at the comment and leave the CI green?

OFC:)

[datapythonista]

Checked quickly, and this does seem to speed up the checkout a bit, from around 28 second to around 22 (not sure if very significant, but nice to use the latest version of the action regardless).

What I see is that if we don't fetch all tags and branches the checkout is almost immediate (like 2 seconds). I think we need them for the release notes, but I'm not aware of anything else that should require them. @ShaharNaveh would you mind having a look and see if the fetch-depth is required for all builds. I don't think anything other than the docs build should need them.

Also, if you want to have a better look at timings, including the ones of the cache action (I didn't check those), that would be great.

[ShaharNaveh]

Checked quickly, and this does seem to speed up the checkout a bit, from around 28 second to around 22 (not sure if very significant, but nice to use the latest version of the action regardless).

What I see is that if we don't fetch all tags and branches the checkout is almost immediate (like 2 seconds). I think we need them for the release notes, but I'm not aware of anything else that should require them. @ShaharNaveh would you mind having a look and see if the fetch-depth is required for all builds. I don't think anything other than the docs build should need them.

@datapythonista The way I decided where each fetch-depth: 0 , was to look at the failed tests in e35cc1b and I added the fetch-depth: 0 wherever there was a failing test.

Also, if you want to have a better look at timings, including the ones of the cache action (I didn't check those), that would be great.

I did see an improvement with the cache, but the difference is 1s.
But the v2 of the cache action is handling the cache with the zstd compression, which means that the cache size can be larger, so I do expect to get an improvement overtime, as the cache will get larger and larger.

[datapythonista]

Thanks for the info @ShaharNaveh. Sounds good. I'd like to understand why we need tags or branches for so many builds, but that's unrelated to this PR.

Thanks for working on this!

[mroeschke]

Thanks @ShaharNaveh

[simonjayhawkins]

We've had several failures in the last couple of days, could there be a compatibility issue with conda-incubator/setup-miniconda@v2 or maybe this was failing before and I didn't notice.

[datapythonista]

We've had several failures in the last couple of days, could there be a compatibility issue with conda-incubator/setup-miniconda@v2 or maybe this was failing before and I didn't notice.

I saw a connection error on conda, are those the failures you are referring to? We can revert, but probably better to try to understand the problem better first.