Build and cache conda environments with lockfiles

[epassaro]

Description

This pull request implement important changes in the test and build-docs workflows:

• Uses the lockfiles to build the environment according to TEP013 bringing more speed and stability to the developers.
  • Every TARDIS commit is identified by a single, reproducible and always working environment. Developers can be sure they are running the same environment as the testing pipeline and other users with the same OS.
  • Faster build times.
• Caches the conda environment with the workflow I submitted to the GitHub Actions Hackathon 2021. My workflow is already used as example in the setup-miniconda action documentation.

  • Faster build times, see the table below.

    OS	Current	Lockfile	Lockfile + Cache
    linux-64	10m 52s	8m 59s	7m 4s
    osx-64	20m 51s	17m 46s	15m 39s

Motivation and context

How has this been tested?

• Testing pipeline
• Other

Examples

Type of change

• Bug fix
• New feature
• Breaking change
• None of the above

Checklist

• I have updated the documentation according to my changes
• I have built the documentation by applying the build_docs label to this pull request (if you don't have enough privileges a reviewer will do it for you)
• I have requested two reviewers for this pull request

[codecov]

Codecov Report

Merging #2011 (d2c1f38) into master (9976a20) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2011   +/-   ##
=======================================
  Coverage   60.01%   60.01%           
=======================================
  Files          70       70           
  Lines        8115     8115           
=======================================
  Hits         4870     4870           
  Misses       3245     3245           

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[tardis-bot]

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The build-docs workflow has succeeded ✔️

Click here to see your results.

[andrewfullard]

How long are environments cached for? Just a specific release cycle?

[epassaro]

How long are environments cached for? Just a specific release cycle?

The cache is scoped to the key and branch, the cache of the default branch is also available to other branches (reference).

The key is formed like this: conda-{platform}-{hash of the lockfile}-{manual cache number}

Then, the cache will not change unless the lockfiles are updated (a release cycle) or manually. We can also add a date to key to reset every 24hs (seems not necessary for us but can be done).