test: Don't enforce BIP94 on regtest unless specified by arg

The added regtest option -test=bip94 is only used in the functional
test for BIP94.
This is done because the default regtest consensus rules
should aim to follow to mainnet, not testnet.

src/chainparams.cpp

@@ -44,6 +44,7 @@ void ReadSigNetArgs(const ArgsManager& args, CChainParams::SigNetOptions& option
 void ReadRegTestArgs(const ArgsManager& args, CChainParams::RegTestOptions& options)
 {
     if (auto value = args.GetBoolArg("-fastprune")) options.fastprune = *value;
+    if (HasTestOption(args, "bip94")) options.enforce_bip94 = true;
 
     for (const std::string& arg : args.GetArgs("-testactivationheight")) {
         const auto found{arg.find('@')};

src/common/args.cpp

@@ -709,6 +709,7 @@ std::string HelpMessageOpt(const std::string &option, const std::string &message
 
 const std::vector<std::string> TEST_OPTIONS_DOC{
     "addrman (use deterministic addrman)",
+    "bip94 (enforce BIP94 consensus rules)",
 };
 
 bool HasTestOption(const ArgsManager& args, const std::string& test_option)

src/kernel/chainparams.cpp

@@ -542,7 +542,7 @@ public:
         consensus.nPowTargetTimespan = 24 * 60 * 60; // one day
         consensus.nPowTargetSpacing = 10 * 60;
         consensus.fPowAllowMinDifficultyBlocks = true;
-        consensus.enforce_BIP94 = true;
+        consensus.enforce_BIP94 = opts.enforce_bip94;
         consensus.fPowNoRetargeting = true;
         consensus.nRuleChangeActivationThreshold = 108; // 75% for testchains
         consensus.nMinerConfirmationWindow = 144; // Faster than normal for regtest (144 instead of 2016)

src/kernel/chainparams.h

@@ -155,6 +155,7 @@ public:
         std::unordered_map<Consensus::DeploymentPos, VersionBitsParameters> version_bits_parameters{};
         std::unordered_map<Consensus::BuriedDeployment, int> activation_heights{};
         bool fastprune{false};
+        bool enforce_bip94{false};
     };
 
     static std::unique_ptr<const CChainParams> RegTest(const RegTestOptions& options);

test/functional/mining_basic.py

@@ -122,6 +122,7 @@ class MiningTest(BitcoinTestFramework):
     def test_timewarp(self):
         self.log.info("Test timewarp attack mitigation (BIP94)")
         node = self.nodes[0]
+        self.restart_node(0, extra_args=['-test=bip94'])
 
         self.log.info("Mine until the last block of the retarget period")
         blockchain_info = self.nodes[0].getblockchaininfo()