Function update_alt_chain_info 

pub fn update_alt_chain_info(
    db: &BlockchainDatabase,
    alt_block_height: &AltBlockHeight,
    prev_hash: &BlockHash,
) -> DbResult<()>

Updates the AltChainInfo with information on a new alt-block.

Panics

This may panic if the block is invalid.

THIS IS NOT ATOMIC