wallet: walk the chain for coins a key owns but the wallet never saw (#88)

A transaction only entered the wallet when its block arrived over the network,
so a key added afterwards was invisible: coins on the chain, private key in
wallet.dat, balance zero. /importwallet has always ended that way -- it writes
the keys and the money never shows up, which looks exactly like a failed import.

ScanForWalletTransactions walks the main chain and hands every transaction that
IsMine() to AddToWalletIfMine, the same two primitives the live path uses. Wired
into /importwallet, and offered as /rescan.

It is also the half that any recovery-phrase feature has to stand on: deriving
keys from twelve words is easy, and without this a restore restores nothing.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/main.h b/src/main.h
index 1d9efac..8d9b7e6 100644
--- a/src/main.h
+++ b/src/main.h
@@ -152,6 +152,11 @@ void TopUpKeyPool();
 vector<unsigned char> GetKeyFromPool();
 bool AddToWallet(const CWalletTx& wtxIn);
 void ReacceptWalletTransactions();
+// Walk the chain from pindexStart forward, adding every transaction that pays
+// a key this wallet holds. Returns how many were added or updated. Needed by
+// anything that puts a key into the wallet after the fact -- an import, a
+// restored backup, and later a recovery phrase.
+int  ScanForWalletTransactions(CBlockIndex* pindexStart);
 // Returns how many wallet transactions the chain corrected.
 int  RescanSpentFlags();
 void RelayWalletTransactions();