Move `CurrentTxVersionInfo` into a new file

Don't compile it for `zcash_script`.

src/Makefile.am

@@ -393,6 +393,7 @@ libbitcoin_common_a_SOURCES = \
   netbase.cpp \
   primitives/block.cpp \
   primitives/transaction.cpp \
+  primitives/tx_version_info.cpp \
   proof_verifier.cpp \
   protocol.cpp \
   pubkey.cpp \
@@ -558,6 +559,7 @@ libzcash_script_la_SOURCES = \
   crypto/sha512.cpp \
   hash.cpp \
   primitives/transaction.cpp \
+  primitives/tx_version_info.cpp \
   pubkey.cpp \
   script/zcash_script.cpp \
   script/interpreter.cpp \

src/primitives/transaction.cpp

@@ -425,45 +425,3 @@ std::string CTransaction::ToString() const
         str += "    " + vout[i].ToString() + "\n";
     return str;
 }
-
-/**
- * Returns the most recent supported transaction version and version group id,
- * as of the specified activation height and active features.
- */
-TxVersionInfo CurrentTxVersionInfo(
-    const Consensus::Params& consensus,
-    int nHeight,
-    bool requireSprout)
-{
-    if (consensus.NetworkUpgradeActive(nHeight, Consensus::UPGRADE_ZFUTURE)) {
-        return {
-            .fOverwintered =   true,
-            .nVersionGroupId = ZFUTURE_VERSION_GROUP_ID,
-            .nVersion =        ZFUTURE_TX_VERSION
-        };
-    } else if (consensus.NetworkUpgradeActive(nHeight, Consensus::UPGRADE_NU5) && !requireSprout) {
-        return {
-            .fOverwintered =   true,
-            .nVersionGroupId = ZIP225_VERSION_GROUP_ID,
-            .nVersion =        ZIP225_TX_VERSION
-        };
-    } else if (consensus.NetworkUpgradeActive(nHeight, Consensus::UPGRADE_SAPLING)) {
-        return {
-            .fOverwintered =   true,
-            .nVersionGroupId = SAPLING_VERSION_GROUP_ID,
-            .nVersion =        SAPLING_TX_VERSION
-        };
-    } else if (consensus.NetworkUpgradeActive(nHeight, Consensus::UPGRADE_OVERWINTER)) {
-        return {
-            .fOverwintered =   true,
-            .nVersionGroupId = OVERWINTER_VERSION_GROUP_ID,
-            .nVersion =        OVERWINTER_TX_VERSION
-        };
-    } else {
-        return {
-            .fOverwintered =   false,
-            .nVersionGroupId = 0,
-            .nVersion =        CTransaction::SPROUT_MIN_CURRENT_VERSION
-        };
-    }
-}

src/primitives/tx_version_info.cpp

@@ -0,0 +1,48 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2014 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or https://www.opensource.org/licenses/mit-license.php .
+
+#include "primitives/transaction.h"
+
+/**
+ * Returns the most recent supported transaction version and version group id,
+ * as of the specified activation height and active features.
+ */
+TxVersionInfo CurrentTxVersionInfo(
+    const Consensus::Params& consensus,
+    int nHeight,
+    bool requireSprout)
+{
+    if (consensus.NetworkUpgradeActive(nHeight, Consensus::UPGRADE_ZFUTURE)) {
+        return {
+            .fOverwintered =   true,
+            .nVersionGroupId = ZFUTURE_VERSION_GROUP_ID,
+            .nVersion =        ZFUTURE_TX_VERSION
+        };
+    } else if (consensus.NetworkUpgradeActive(nHeight, Consensus::UPGRADE_NU5) && !requireSprout) {
+        return {
+            .fOverwintered =   true,
+            .nVersionGroupId = ZIP225_VERSION_GROUP_ID,
+            .nVersion =        ZIP225_TX_VERSION
+        };
+    } else if (consensus.NetworkUpgradeActive(nHeight, Consensus::UPGRADE_SAPLING)) {
+        return {
+            .fOverwintered =   true,
+            .nVersionGroupId = SAPLING_VERSION_GROUP_ID,
+            .nVersion =        SAPLING_TX_VERSION
+        };
+    } else if (consensus.NetworkUpgradeActive(nHeight, Consensus::UPGRADE_OVERWINTER)) {
+        return {
+            .fOverwintered =   true,
+            .nVersionGroupId = OVERWINTER_VERSION_GROUP_ID,
+            .nVersion =        OVERWINTER_TX_VERSION
+        };
+    } else {
+        return {
+            .fOverwintered =   false,
+            .nVersionGroupId = 0,
+            .nVersion =        CTransaction::SPROUT_MIN_CURRENT_VERSION
+        };
+    }
+}