Introduce the NonFungibleTokensV1_1 amendment:

The XLS-20 implementation contained two bugs that would require the
introduction of amendments. This complicates the adoption of XLS-20
by requiring a staggered amendment activation, first of the two fix
amendments, followed by the `NonFungibleTokensV1` amendment.

After consideration, the consensus among node operators is that the
process should be simplified by the introduction of a new amendment
that, if enabled, would behaves as if the `NonFungibleTokensV1` and
the two fix amendments (`fixNFTokenDirV1` and `fixNFTokenNegOffer`)
were activated at once.

This commit implements this proposal; it does not introduce any new
functionality or additional features, above and beyond that offered
by the existing amendments.

src/ripple/protocol/Feature.h

@@ -337,6 +337,7 @@ extern uint256 const featureNonFungibleTokensV1;
 extern uint256 const featureExpandedSignerList;
 extern uint256 const fixNFTokenDirV1;
 extern uint256 const fixNFTokenNegOffer;
+extern uint256 const featureNonFungibleTokensV1_1;
 
 }  // namespace ripple
 

src/ripple/protocol/impl/Feature.cpp

@@ -441,6 +441,7 @@ REGISTER_FEATURE(NonFungibleTokensV1,           Supported::yes, DefaultVote::no)
 REGISTER_FEATURE(ExpandedSignerList,            Supported::yes, DefaultVote::no);
 REGISTER_FIX    (fixNFTokenDirV1,               Supported::yes, DefaultVote::no);
 REGISTER_FIX    (fixNFTokenNegOffer,            Supported::yes, DefaultVote::no);
+REGISTER_FEATURE(NonFungibleTokensV1_1,         Supported::yes, DefaultVote::no);
 
 // The following amendments have been active for at least two years. Their
 // pre-amendment code has been removed and the identifiers are deprecated.

src/ripple/protocol/impl/Rules.cpp

@@ -17,10 +17,10 @@
 */
 //==============================================================================
 
+#include <ripple/protocol/Feature.h>
+//#include <ripple/protocol/Indexes.h>
 #include <ripple/protocol/Rules.h>
 
-#include <ripple/protocol/Indexes.h>
-
 namespace ripple {
 
 class Rules::Impl
@@ -40,9 +40,8 @@ class Rules::Impl
         std::unordered_set<uint256, beast::uhash<>> const& presets,
         std::optional<uint256> const& digest,
         STVector256 const& amendments)
-        : presets_(presets)
+        : presets_(presets), digest_(digest)
     {
-        digest_ = digest;
         set_.reserve(amendments.size());
         set_.insert(amendments.begin(), amendments.end());
     }
@@ -83,6 +82,18 @@ bool
 Rules::enabled(uint256 const& feature) const
 {
     assert(impl_);
+
+    // The functionality of the "NonFungibleTokensV1_1" amendment is
+    // precisely the functionality of the following three amendments
+    // so if their status is ever queried individually, we inject an
+    // extra check here to simplify the checking elsewhere.
+    if (feature == featureNonFungibleTokensV1 ||
+        feature == fixNFTokenNegOffer || feature == fixNFTokenDirV1)
+    {
+        if (impl_->enabled(featureNonFungibleTokensV1_1))
+            return true;
+    }
+
     return impl_->enabled(feature);
 }