add way to get CI builds for a specific commit

[simeonschaub]

I often find it useful to use to directly download the CI build outputs when reviewing a PR to base. My usual workflow is to click on Details on the particular tester for my platform, go to the Build Properties tab and copy the download_url there. I then download that tarball, extract it and run it. It would be really nice if I could just do juliaup add <git commit SHA> and juliaup did everything else for me, even clean it up once I don't need it anymore. I think this should be possible since the corresponding download URLs (I think?) all follow the same scheme based on the commit hash.

[johnnychen94]

This is now implemented in jill.py in https://github.com/johnnychen94/jill.py/pull/89 and I'd like to give a summary here so if someone is going to implement this in juliaup he doesn't need to redo everything from scratch.

• Specific commit build is very temporary so there should be a GC functionality to automatically clean them up. In jill.py I choose to install the dev build into julia-dev folder and so every time when users do jill install 1.8.0+cc4be25c, it overrides the previous dev build contents. Thus made an auto GC.
• Instead of keeping the entire Julia repo and use git command to query the hash, I use GitHub API to fetch the complete commit hash and then map it to the Julia-flavored one (the first 10 characters). See the codes here
• There are four possible channels(buckets) to fetch CI builds: assert_pretesting, pretesting, assert_bin, and bin. See my configuration here