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If the commit missing the signoff is on a non-main branch (eg merge in the example above), and you are a Besu maintainer, you should be able to force-push to that branch (eg revert rollback the most recent commit).
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The sign off needs to be using your legal name, not a pseudonym. Git has a built-in mechanism to allow this with the -s or --signoff argument to git commit command, providing your user.name and user.email have been setup correctly.
If you have any questions, you can reach us on Besu chat.Discord