rpc: Document all aliases for first arg of listtransactions

src/wallet/rpcwallet.cpp

@@ -1399,7 +1399,7 @@ UniValue listtransactions(const JSONRPCRequest& request)
                 "\nIf a label name is provided, this will return only incoming transactions paying to addresses with the specified label.\n"
                 "\nReturns up to 'count' most recent transactions skipping the first 'from' transactions.\n",
                 {
-                    {"label", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "If set, should be a valid label name to return only incoming transactions\n"
+                    {"label|dummy", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "If set, should be a valid label name to return only incoming transactions\n"
                           "with the specified label, or \"*\" to disable filtering and return all transactions."},
                     {"count", RPCArg::Type::NUM, /* default */ "10", "The number of transactions to return"},
                     {"skip", RPCArg::Type::NUM, /* default */ "0", "The number of transactions to skip"},

test/functional/wallet_listtransactions.py

@@ -97,6 +97,8 @@ class ListTransactionsTest(BitcoinTestFramework):
         txid = self.nodes[1].sendtoaddress(multisig["address"], 0.1)
         self.nodes[1].generate(1)
         self.sync_all()
+        assert_equal(len(self.nodes[0].listtransactions(label="watchonly", include_watchonly=True)), 1)
+        assert_equal(len(self.nodes[0].listtransactions(dummy="watchonly", include_watchonly=True)), 1)
         assert len(self.nodes[0].listtransactions(label="watchonly", count=100, include_watchonly=False)) == 0
         assert_array_result(self.nodes[0].listtransactions(label="watchonly", count=100, include_watchonly=True),
                             {"category": "receive", "amount": Decimal("0.1")},