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Discussion in Feb 28 contributor call on enabling the merge queue 2023-02-28 Contributor Call - APAC Friendly Time after 23.1.1 release
Note - it's part of "branch protection" - so you turn it on for specific branch protection rules.
This feature is still in beta - discussion https://github.blog/changelog/2023-02-08-pull-request-merge-queue-public-beta/
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