fix(core): prevent --set-head startup rewind overshooting to N-1, close #2465

[gzliudan]

Proposed changes

Fix issue #2465: an off-by-one boundary in startup repair when RollbackNumber is set from --set-head.

Repair now accepts the target height (<=) so startup does not rewind past N and fail with 'can't rollback to N which is greater than current N-1'.

Add a regression test to ensure startup repair stops at the requested rollback block when state exists.

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• test: Adding missing tests or correcting existing tests

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• Consensus
• Account
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• Geth
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Checklist

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• This PR has sufficient test coverage (unit/integration test) OR I have provided reason in the PR description for not having test coverage
• Tested on a private network from the genesis block and monitored the chain operating correctly for multiple epochs.
• Provide an end-to-end test plan in the PR description on how to manually test it on the devnet/testnet.
• Tested the backwards compatibility.
• Tested with XDC nodes running this version co-exist with those running the previous version.
• Relevant documentation has been updated as part of this PR
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[Copilot]

Pull request overview

Fixes an off-by-one boundary in the blockchain startup repair path when --set-head (via common.RollbackNumber) is set, preventing the repair rewind loop from overshooting the intended rollback target and causing a fatal “can’t rollback … greater than current …” error.

Changes:

• Adjust BlockChain.repair termination condition to include the rollback target height (<=), so repair can stop exactly at the requested block when state is available.
• Add a regression test to ensure startup repair respects the rollback target and does not rewind below it when the target state exists.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
core/blockchain.go	Fix off-by-one in startup repair rewind boundary when common.RollbackNumber is set.
core/blockchain_test.go	Add regression test validating repair stops at the rollback target when state exists.