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Pull request overview
Updates CI checkout/fetch behavior to avoid fatal: no merge base failures on fork PRs by switching those runs to a full Git history.
Changes:
- Detect fork PRs by comparing
head.repo.full_nameandbase.repo.full_name. - Use
fetch-depth: 0for fork PRs while retaining shallow fetch for same-repo PRs. - Adjust base SHA fetching to avoid shallow-history merge-base failures on fork PRs.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| changes/9617.fix.md | Adds a changelog entry describing the CI fix. |
| .github/workflows/ci.yml | Implements fork PR detection and conditionally uses full clone / non-shallow base SHA fetch. |
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HyeockJinKim
requested changes
Mar 5, 2026
fregataa
changed the title
fregataa
changed the title
Fork PRs have diverged history from upstream, so the shallow fetch (PR commits + 1) doesn't include enough common ancestors for git merge-base to work. Detect fork PRs by comparing head and base repo names, and use fetch-depth: 0 for full history in that case. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Compute IS_FORK_PR once in the "Calculate the fetch depth" step of each job (lint-and-typecheck, test) and reference the env var in subsequent steps instead of repeating the full_name comparison. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
fatal: no merge baseerrorhead.repo.full_namevsbase.repo.full_namefetch-depth: 0(full clone) for fork PRs in bothlint-and-typecheckandtestjobs, while preserving the existing shallow clone optimization for same-repo PRsWhy full clone instead of requiring fork sync?
Fork PRs may diverge far from upstream, making the shallow clone's history insufficient to find a merge base. While contributors could sync their fork before submitting, requiring this adds unnecessary friction for external contributors. The CI should work regardless of how far the fork has diverged.
Test plan
pants --changed-sincesucceedsResolves BA-4852