refactor: a new constant with Tx Version

src/primitives/transaction.h

@@ -184,12 +184,14 @@ class CTransaction
 public:
     // Default transaction version.
     static const int32_t CURRENT_VERSION=2;
+    // Special transaction version
+    static const int32_t SPECIAL_VERSION = 3;
 
     // Changing the default transaction version requires a two step process: first
     // adapting relay policy by bumping MAX_STANDARD_VERSION, and then later date
     // bumping the default CURRENT_VERSION at which point both CURRENT_VERSION and
     // MAX_STANDARD_VERSION will be equal.
-    static const int32_t MAX_STANDARD_VERSION=3;
+    static const int32_t MAX_STANDARD_VERSION = SPECIAL_VERSION;
 
     // The local variables are made const to prevent unintended modification
     // without updating the cached hash value. However, CTransaction is not
@@ -268,7 +270,7 @@ class CTransaction
 
     bool IsSpecialTxVersion() const noexcept
     {
-        return nVersion >= 3;
+        return nVersion >= SPECIAL_VERSION;
     }
 
     bool HasExtraPayloadField() const noexcept
@@ -298,7 +300,7 @@ struct CMutableTransaction
         SER_READ(obj, obj.nVersion = (int16_t) (n32bitVersion & 0xffff));
         SER_READ(obj, obj.nType = (uint16_t) ((n32bitVersion >> 16) & 0xffff));
         READWRITE(obj.vin, obj.vout, obj.nLockTime);
-        if (obj.nVersion >= 3 && obj.nType != TRANSACTION_NORMAL) {
+        if (obj.nVersion >= CTransaction::SPECIAL_VERSION && obj.nType != TRANSACTION_NORMAL) {
             READWRITE(obj.vExtraPayload);
         }
     }

src/script/interpreter.cpp

@@ -1476,7 +1476,7 @@ class CTransactionSignatureSerializer
              SerializeOutput(s, nOutput);
         // Serialize nLockTime
         ::Serialize(s, txTo.nLockTime);
-        if (txTo.nVersion >= 3 && txTo.nType != TRANSACTION_NORMAL)
+        if (txTo.nVersion >= CTransaction::SPECIAL_VERSION && txTo.nType != TRANSACTION_NORMAL)
             ::Serialize(s, txTo.vExtraPayload);
     }
 };