Pull requests from a fork can no longer be rebased

Rebasing a pull request that comes from a fork required Mergify to impersonate a GitHub user and force-push the fork’s branch, because GitHub refuses an OAuth token on its rebase API for a fork. That capability was deprecated for removal on July 1, 2026, and it has now been removed.

A rebase action or an @mergifyio rebase command on a pull request from a fork now fails with a check run that explains why. Use the update action or the @mergifyio update command on those instead: it brings the pull request up to date by merging the base branch into it, and needs no impersonation. If the branch has to keep a linear history, its author has to rebase it themselves.

This applies whether or not bot_account is set: the rebase impersonated a user either way, falling back to the pull request author or to whoever sent the command. Rebases with autosquash: true are not affected.