ZeroB2M amendment (#293)

* ZeroB2M amendment

Co-authored-by: Denis Angell <dangell@transia.co>

src/ripple/app/tx/impl/Import.cpp

@@ -1224,7 +1224,13 @@ Import::doApply()
         create ? STAmount(bonusAmount) : STAmount(mSourceBalance);
 
     uint64_t creditDrops = burn.xrp().drops();
-    if (elapsed < 2'000'000)
+
+    if (view().rules().enabled(featureZeroB2M))
+    {
+        // B2M xrp is disabled by amendment
+        creditDrops = 0;
+    }
+    else if (elapsed < 2'000'000)
     {
         // first 2MM ledgers
         // the ratio is 1:1

src/ripple/protocol/Feature.h

@@ -74,7 +74,7 @@ namespace detail {
 // Feature.cpp. Because it's only used to reserve storage, and determine how
 // large to make the FeatureBitset, it MAY be larger. It MUST NOT be less than
 // the actual number of amendments. A LogicError on startup will verify this.
-static constexpr std::size_t numFeatures = 68;
+static constexpr std::size_t numFeatures = 69;
 
 /** Amendments that this server supports and the default voting behavior.
    Whether they are enabled depends on the Rules defined in the validated
@@ -356,6 +356,7 @@ extern uint256 const featureHooksUpdate1;
 extern uint256 const fixXahauV1;
 extern uint256 const fixXahauV2;
 extern uint256 const featureRemit;
+extern uint256 const featureZeroB2M;
 
 }  // namespace ripple
 

src/ripple/protocol/impl/Feature.cpp

@@ -462,6 +462,7 @@ REGISTER_FEATURE(HooksUpdate1,                  Supported::yes, VoteBehavior::De
 REGISTER_FIX    (fixXahauV1,                    Supported::yes, VoteBehavior::DefaultNo);
 REGISTER_FIX    (fixXahauV2,                    Supported::yes, VoteBehavior::DefaultNo);
 REGISTER_FEATURE(Remit,                         Supported::yes, VoteBehavior::DefaultNo);
+REGISTER_FEATURE(ZeroB2M,                       Supported::yes, VoteBehavior::DefaultNo);
 
 // The following amendments are obsolete, but must remain supported
 // because they could potentially get enabled.