ci: build interop Docker image for pushes to master, and for releases

[marten-seemann]

This PR:

1. Builds a new interop Docker image for every push to master, so that the interop runner can always test the most recent image
2. Tags an image for releases. Those won't be picked up by the interop runner, but can be useful for debugging.

[marten-seemann]

@galargh Could you take a look at this PR, especially the code path for releases? I don't really know how to test this, and you have a lot more experience with GHA workflows. Thank you!

[codecov]

Codecov Report

Merging #4035 (b12c261) into master (83c00a5) will increase coverage by 0.64%.
Report is 10 commits behind head on master.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4035      +/-   ##
==========================================
+ Coverage   82.94%   83.58%   +0.64%     
==========================================
  Files         147      147              
  Lines       14781    15120     +339     
==========================================
+ Hits        12260    12638     +378     
+ Misses       2023     1988      -35     
+ Partials      498      494       -4     

see 14 files with indirect coverage changes

[galargh]

With workflows like this one, I usually try running it on real triggers in a fork. If you're cool with the changes I proposed, I can try doing that for this repo before we merge.

[galargh]

How are the tags for this repo created? I'm asking because if they're created automatically with the default GitHub Actions token then this trigger won't work unfortunately. There are some workarounds for that though.

[marten-seemann]

Currently I'm pushing them manually, but I was considering adopting the uCI release workflow.
How would those workaround work?

[galargh]

With uCI release workflows, we'd need to add a workflow_run trigger (for successful release workflow runs) to this job and then use https://github.com/pl-strflt/uci/tree/main/.github/actions/inspect-releaser to retrieve information about the release that the release workflow possibly created. You can ping me when you want to set it up, happy to help :)

[marten-seemann]

I tried it out in https://github.com/quic-go/docker-test, and it seems to work:

Thank you for your help @galargh!