Merge bitcoin/bitcoin#25439: rpc: Return incrementalrelayfee in getmempoolinfo

fafee78 rpc: Return incrementalrelayfee in getmempoolinfo (MacroFake)

Pull request description:

  Seems odd to return other policy info, but not the incremental relay fee

ACKs for top commit:
  1440000bytes:
    ACK bitcoin/bitcoin@fafee78
  w0xlt:
    Code Review ACK bitcoin/bitcoin@fafee78
  jarolrod:
    tACK fafee78

Tree-SHA512: faad0af6c039b8257acbeac913bc5dcdb2ea2db304c95e52601536c8de60eb1186e9fbb4a64a68adf476605f18022aeda16a5644a0d7912592b0977e4c029638

Author: MacroFake

src/rpc/mempool.cpp

@@ -661,14 +661,15 @@ UniValue MempoolInfoToJSON(const CTxMemPool& pool)
     ret.pushKV("maxmempool", maxmempool);
     ret.pushKV("mempoolminfee", ValueFromAmount(std::max(pool.GetMinFee(maxmempool), ::minRelayTxFee).GetFeePerK()));
     ret.pushKV("minrelaytxfee", ValueFromAmount(::minRelayTxFee.GetFeePerK()));
+    ret.pushKV("incrementalrelayfee", ValueFromAmount(::incrementalRelayFee.GetFeePerK()));
     ret.pushKV("unbroadcastcount", uint64_t{pool.GetUnbroadcastTxs().size()});
     return ret;
 }
 
 static RPCHelpMan getmempoolinfo()
 {
     return RPCHelpMan{"getmempoolinfo",
-        "\nReturns details on the active state of the TX memory pool.\n",
+        "Returns details on the active state of the TX memory pool.",
         {},
         RPCResult{
             RPCResult::Type::OBJ, "", "",
@@ -681,7 +682,8 @@ static RPCHelpMan getmempoolinfo()
                 {RPCResult::Type::NUM, "maxmempool", "Maximum memory usage for the mempool"},
                 {RPCResult::Type::STR_AMOUNT, "mempoolminfee", "Minimum fee rate in " + CURRENCY_UNIT + "/kvB for tx to be accepted. Is the maximum of minrelaytxfee and minimum mempool fee"},
                 {RPCResult::Type::STR_AMOUNT, "minrelaytxfee", "Current minimum relay fee for transactions"},
-                {RPCResult::Type::NUM, "unbroadcastcount", "Current number of transactions that haven't passed initial broadcast yet"}
+                {RPCResult::Type::NUM, "incrementalrelayfee", "minimum fee rate increment for mempool limiting or BIP 125 replacement in " + CURRENCY_UNIT + "/kvB"},
+                {RPCResult::Type::NUM, "unbroadcastcount", "Current number of transactions that haven't passed initial broadcast yet"},
             }},
         RPCExamples{
             HelpExampleCli("getmempoolinfo", "")

test/functional/feature_rbf.py

@@ -711,6 +711,7 @@ def test_replacement_relay_fee(self):
 
         # Higher fee, higher feerate, different txid, but the replacement does not provide a relay
         # fee conforming to node's `incrementalrelayfee` policy of 1000 sat per KB.
+        assert_equal(self.nodes[0].getmempoolinfo()["incrementalrelayfee"], Decimal("0.00001"))
         tx.vout[0].nValue -= 1
         assert_raises_rpc_error(-26, "insufficient fee", self.nodes[0].sendrawtransaction, tx.serialize().hex())