Build context resolved as remote git checkout -> Git LFS pointer files in build context (refs docker/bake-action#488)

[zeckson]

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• I've read the contributing guidelines and wholeheartedly agree. I've also read the issue reporting guide.

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• I have found a bug that the documentation does not mention anything about my problem
• I have found a bug that there are no open or closed issues that are related to my problem
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Description of bug

Bug description

When using docker/setup-buildx-action@v4 + docker/bake-action@v7 in GitHub Actions, a build context that points to a subdirectory containing Git LFS-tracked files gets resolved by BuildKit as a remote git context. This bypasses Git LFS smudge filters and exposes pointer files (containing "version https://git-lfs.github.com/spec/v1") inside the build context, causing builds to fail when Dockerfiles detect pointer files.

Environment

• Workflow: https://github.com/zeckson/mykapitel.ru (.github/workflows/smoke-test.yml)
• Actions: actions/checkout@v6 (with lfs: true), docker/setup-buildx-action@v4, docker/bake-action@v7
• Works with: setup-buildx-action@v3 + bake-action@v5

Reproduction steps

1. Use actions/checkout@v6 with lfs: true so runner workspace has smudged LFS files.
2. Set up buildx using docker/setup-buildx-action@v4 and invoke docker/bake-action@v7 with context pointing to a subdirectory (e.g., ./docker).
3. BuildKit/bake resolves the subdirectory context via a remote git fetch which returns raw Git LFS pointer files instead of smudged objects.

Expected

• When the runner workspace already has LFS objects checked out, bake/buildx should use the local smudged files for a local workspace context or offer a clear option to force local context usage so builds do not inadvertently use remote git checkouts that skip smudge filters.

Observed

• The file seen inside the build context is a Git LFS pointer and the build fails (example: "Error: akeeba-backup.zip is a Git LFS pointer, not the actual file.").

Failure log excerpt

• COPY docker/akeeba-backup.zip /tmp/backup.zip
• RUN if grep -q "version https://git-lfs.github.com/spec/v1" /tmp/backup.zip; then echo "Error: akeeba-backup.zip is a Git LFS pointer, not the actual file." && exit 1; fi && unzip -t /tmp/backup.zip && unzip /tmp/backup.zip -d /app && rm /tmp/backup.zip

Additional info

• Full failing run: https://github.com/zeckson/mykapitel.ru/actions/runs/30447565481
• Original report: Build with setup-buildx-action@v4 + bake-action@v7 uses remote git context -> Git LFS pointer files in build context docker/bake-action#488

I can provide the exact workflow file, Dockerfile from the failing run, or open a minimal repro PR if that helps.

[tonistiigi]

I don't think we have immediate plan to support LFS. You can use path context in back-action to use the checkout from action/checkout https://github.com/docker/bake-action#path-context