Auto unassigner

[jimchamp]

Closes #8704

Creates GitHub action workflow that automatically removes assignees from issues if they have been assigned for too long without opening a linked pull request. A comment is left on the issue thread whenever an assignee is removed.

This workflow is scheduled to run 30 minutes before the new comment update, so we should have visibility on issues that have been automatically updated.

Important

This action only reads and modifies issues in the repository that triggered the action.

Technical

General flow of script:

1. Parse command-line arguments.
2. Fetch all open issues that have assignees.
3. Filter out unaffected issues, and flag excluded assignees.
4. Remove non-excluded assignees from the remaining filtered issues.

Script makes use of the octokit/action.js API client, which automatically handles authentication in GitHub workflows.

Testing

Screenshot

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