fix: failed to reorg when only one stale block

[yangby-cryptape]

Description

This is a contract issue:

• When update Bitcoin SPV instance:

  Cell Deps:
  - Type Lock
  - SPV Client (id=k)
  - ... ...
  Inputs:
  - SPV Info (tip_client_id=k)
  - SPV Client (id=k+1)
  - ... ...
  Outputs:
  - SPV Info (tip_client_id=k+1)
  - SPV Client (id=k+1)
  - ... ...
  Witnesses:
  - SPV Update
  - ... ...

• When reorg Bitcoin SPV instance when only 1 stale block:

  Cell Deps:
  - Type Lock
  - SPV Client (id=k)
  - ... ...
  Inputs:
  - SPV Info (tip_client_id=k+1)
  - SPV Client (id=k+1)
  - ... ...
  Outputs:
  - SPV Info (tip_client_id=k+1)
  - SPV Client (id=k+1)
  - ... ...
  Witnesses:
  - SPV Update
  - ... ...

They have exactly the same structure, but different tip-client-id in the SPV info cell.

So, the contract couldn't distinguish the operation for them.

Solution (Urgent, maybe Temporary)

Reorg two Bitcoin SPV clients when they are only 1 stale block.

PROS:

• Quick to apply the patch, don't have to re-deploy the contract.

CONS:

• Larger transaction, causes a bit more fee.

My Own Opionion

I think it may be a good final solution.

Since update and reorg-1 are so similar, and reorg are small probability events, adding a tag to all operations is not a good deal.