feat: fetch fork PR head from base repo in the merge checkout strategy - #6743
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meringu wants to merge 1 commit into
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feat: fetch fork PR head from base repo in the merge checkout strategy#6743meringu wants to merge 1 commit into
meringu wants to merge 1 commit into
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In the merge checkout strategy Atlantis clones the base branch and merges the PR head into it. The head was fetched from the PR's "source" remote (the head repo, e.g. a fork), which requires access to the fork — a problem when the GitHub App isn't installed on the fork, or the token is scoped to the base repo. GitHub exposes every PR's head on the base repo as refs/pull/<n>/head, which the App path already uses. Extend that to the merge strategy: when merging a GitHub PR, fetch pull/<n>/head from origin instead of the fork's remote. This lets fork PRs run in merge mode without access to the fork. It is a no-op for same-repo PRs (same commit), and unchanged for the branch strategy and non-GitHub hosts. Signed-off-by: Henry Muru Paenga <meringu@gmail.com>
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In the merge checkout strategy Atlantis clones the base branch and merges the PR head into it. The head was fetched from the PR's "source" remote (the head repo, e.g. a fork), which requires access to the fork — a problem when the GitHub App isn't installed on the fork, or the token is scoped to the base repo.
GitHub exposes every PR's head on the base repo as refs/pull//head, which the App path already uses. Extend that to the merge strategy: when merging a GitHub PR, fetch pull//head from origin instead of the fork's remote. This lets fork PRs run in merge mode without access to the fork. It is a no-op for same-repo PRs (same commit), and unchanged for the branch strategy and non-GitHub hosts.
This is what is needed to support forks in our environments. We run a controller app that issues scoped tokens from a single GitHub app to many hundreds of Atlantis instances. It is using app token, but the Atlantis instance isn't configured to run as an app. This token issuing process allows us to scale the provisioning of Atlantis instances in our org.