Support GitHub Actions

[vinsidious]

Overview

This PR adds support for running release-it on GitHub Actions and fixes #618.

Background

When running on GitHub Actions, GitHub injects the GITHUB_TOKEN environment variable automatically. This token differs from typical GitHub user tokens in the following ways:

• It has a predefined list of permissions
• It is unique to the job being run and expires after 60 minutes
• It is not tied to a user

Because of this, we need to skip the user authentication and collaborator checks when we're running on GitHub Actions.

Example of this running successfully

[webpro]

Thanks, @vinsidious! What's the reason you made the variable part of the global config? I think we can/should keep its scope entirely within the GitHub plugin.

[vinsidious]

@webpro I actually went back and forth with that decision. I think my rationale was: if the execution environment was within a GitHub Action, that's on the global level and sort of pervades every other action/plugin.

That being said, you obviously have way more context here and I also agree with you. I'll make the change 👍

[webpro]

Makes total sense. But I think e.g. the npm plugin is not interested in this. If this ever changes we can of course move it up again.

[vinsidious]

@webpro Hopefully this is what you had in mind? Please let me know if this isn't the right approach

[vinsidious]

@webpro Looks like the tests are passing but I do want to call out that I've noticed them being a little iffy. I imagine it has something to do with ava's concurrency but appending .serial to the suspect test cases didn't seem to help very much.

[webpro]

@vinsidious Do you recall what kind of errors you were seeing? I'm on macOS, so if you're using something different this might be useful info.

[vinsidious]

I'm on macOS as well, but the logs from the failed tests on GitHub are the same as the errors I was getting locally. I was able to consistently repro by commenting/uncommenting the line that sets process.env.GITHUB_ACTION = 'foo-123'

[webpro]

Thanks a lot, @vinsidious! Merged and released as v13.2.0-beta.0.