Merge #12950: bitcoin-tx: Flatten for loop over one element

fa72f34 bitcoin-tx: Remove unused for loop (MarcoFalke)

Pull request description:

  This flattens out a for loop and gets rid of the then unused vector `txVariants`.

Tree-SHA512: 68081b313d846ce235a97a642c9d0097c3641350e819d6254001f332b053e41fa63ce49faca68120f5aaf5d5f4bfda104662eae781e2956d76a8915770344045

src/bitcoin-tx.cpp

@@ -545,12 +545,10 @@ static void MutateTxSign(CMutableTransaction& tx, const std::string& flagStr)
         if (!findSighashFlags(nHashType, flagStr))
             throw std::runtime_error("unknown sighash flag/sign option");
 
-    std::vector<CTransaction> txVariants;
-    txVariants.push_back(tx);
-
     // mergedTx will end up with all the signatures; it
     // starts as a clone of the raw tx:
-    CMutableTransaction mergedTx(txVariants[0]);
+    CMutableTransaction mergedTx{tx};
+    const CTransaction txv{tx};
     CCoinsView viewDummy;
     CCoinsViewCache view(&viewDummy);
 
@@ -633,7 +631,7 @@ static void MutateTxSign(CMutableTransaction& tx, const std::string& flagStr)
 
     // Sign what we can:
     for (unsigned int i = 0; i < mergedTx.vin.size(); i++) {
-        CTxIn& txin = mergedTx.vin[i];
+        const CTxIn& txin = mergedTx.vin[i];
         const Coin& coin = view.AccessCoin(txin.prevout);
         if (coin.IsSpent()) {
             continue;
@@ -647,8 +645,7 @@ static void MutateTxSign(CMutableTransaction& tx, const std::string& flagStr)
             ProduceSignature(keystore, MutableTransactionSignatureCreator(&mergedTx, i, amount, nHashType), prevPubKey, sigdata);
 
         // ... and merge in other signatures:
-        for (const CTransaction& txv : txVariants)
-            sigdata = CombineSignatures(prevPubKey, MutableTransactionSignatureChecker(&mergedTx, i, amount), sigdata, DataFromTransaction(txv, i));
+        sigdata = CombineSignatures(prevPubKey, MutableTransactionSignatureChecker(&mergedTx, i, amount), sigdata, DataFromTransaction(txv, i));
         UpdateTransaction(mergedTx, i, sigdata);
     }