Clear disconnected transactions.

Rather than removing disconnected transactions from the node viewpoint
transaction store, clear the entry instead.  This is needed for the
connect code to update transactions that were removed on the other side of
a chain fork.

txlookup.go

@@ -60,22 +60,31 @@ func connectTransactions(txStore map[btcwire.ShaHash]*txData, block *btcutil.Blo
 // transactions in the passed map are updated.
 func disconnectTransactions(txStore map[btcwire.ShaHash]*txData, block *btcutil.Block) error {
 	// Loop through all of the transactions in the block to see if any of
-	// them are ones were need to undo based on the results map.
+	// them are ones that need to be undone based on the transaction store.
 	for i, tx := range block.MsgBlock().Transactions {
 		txHash, err := block.TxSha(i)
 		if err != nil {
 			return err
 		}
 
-		// Remove this transaction from the transaction store (this is a
-		// no-op if it's not there).
-		delete(txStore, *txHash)
+		// Clear this transaction from the transaction store if needed.
+		// Only clear it rather than deleting it because the transaction
+		// connect code relies on its presence to decide whether or not
+		// to update the store and any transactions which exist on both
+		// sides of a fork would otherwise not be updated.
+		if txD, exists := txStore[*txHash]; exists {
+			txD.tx = nil
+			txD.blockHeight = 0
+			txD.spent = nil
+			txD.err = btcdb.TxShaMissing
+		}
 
 		// Unspend the origin transaction output.
 		for _, txIn := range tx.TxIn {
 			originHash := &txIn.PreviousOutpoint.Hash
 			originIndex := txIn.PreviousOutpoint.Index
-			if originTx, exists := txStore[*originHash]; exists {
+			originTx, exists := txStore[*originHash]
+			if exists && originTx.tx != nil && originTx.err == nil {
 				originTx.spent[originIndex] = false
 			}
 		}