git: fix potential difference between cache and snapshot #6281
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Signed-off-by: Tonis Tiigi <[email protected]>
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crazy-max
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Oct 13, 2025
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If content changes in the upstream Git repository, there is a theoretical race between computing the cache key for ref(based on commit SHA) and actually checking out that ref. If commit changes in between these operations then the content may be cached by wrong commit SHA and wrong commit SHA can also end up in the provenance attestation.
This fix detects this case. If the original commit from the cache computation is still available in upstream then that commit is used instead (it is not the correct commit anymore but it was in the start of the build so it can still be trusted). If upstream has removed the commit, then the build fails and needs to be restarted.