In the log I see things like:

    2017-09-13 03:54:33 init message: Rescanning...
    2017-09-13 03:54:33 Rescanning last 68616 blocks (from block 416339)...
    2017-09-13 03:54:40 AddToWallet xxxxx  update
    2017-09-13 03:55:33 Still rescanning. At block 418849. Progress=0.549138

I would be interested to see the wallet file name on each of these log lines.

Would there be any interest in merging such a PR?
* If fUpdate is true, existing transactions will be updated.
     * TODO: One exception to this is that the abandoned state is cleared under the
     * assumption that any further notification of a transaction that was considered
     * abandoned is an indication that it is not safe to be considered abandoned.
     * Abandoned state should probably be more carefully tracked via different
     * posInBlock signals or by checking mempool presence when necessary.
     */
    bool AddToWalletIfInvolvingMe(const CTransactionRef& tx, const CBlockIndex* pIndex, int posInBlock, bool fUpdate) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    
    void MarkConflicted(const uint256& hashBlock, const uint256& hashTx);
    
    void MarkInputsDirty(const CTransactionRef& tx);
    void SyncMetaData(std::pair<TxSpends::iterator, TxSpends::iterator>);
    /* Used by TransactionAddedToMemorypool/BlockConnected/Disconnected/ScanForWalletTransactions.
     * Should be called with pindexBlock and posInBlock if this is for a transaction that is included in a block. */
    void SyncTransaction(const CTransactionRef& tx, const CBlockIndex *pindex = nullptr, int posInBlock = 0, bool update_tx = true) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    
    CHDChain hdChain;
    
    void DeriveNewChildKey(WalletBatch &batch, CKeyMetadata& metadata, CKey& secret, bool internal = false) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    std::set<int64_t> setInternalKeyPool;
    std::set<int64_t> setExternalKeyPool;
    std::set<int64_t> set_pre_split_keypool;
    int64_t m_max_keypool_index = 0;
    std::map<CKeyID, int64_t> m_pool_key_to_index;
    std::atomic<uint64_t> m_wallet_flags{0};
    int64_t nTimeFirstKey = 0;
    /**
     * Private version of AddWatchOnly method which does not accept a
     * timestamp, and which will reset the wallet's nTimeFirstKey value to 1 if