Merge bitcoin/bitcoin#25775: docs: remove non-signaling mentions of BIP125

1dc03dda05e9dce128e57f05bb7b1bb02b3cfb9e [doc] remove non-signaling mentions of BIP125 (glozow)
32024d40f03fbf47c64d814fa5f2c2a73ec14cb7 scripted-diff: remove mention of BIP125 from non-signaling var names (glozow)

Pull request description:

  We have pretty thorough documentation of our RBF policy in doc/policy/mempool-replacements.md. It enumerates each rule with several sentences of rationale. Also, each rule pretty much has its own function (3 and 4 share one), with extensive comments. The doc states explicitly that our rules are similar but differ from BIP125, and contains a record of historical changes to RBF policy.

  We should not use "BIP125" as synonymous with our RBF policy because:
  - Our RBF policy is different from what is specified in BIP125, for example:
      - the BIP does not mention our rule about the replacement feerate being higher (our Rule 6)
      - the BIP uses minimum relay feerate for Rule 4, while we have used incremental relay feerate since #9380
      - the "inherited signaling" question (CVE-2021-31876). Call it discrepancy, ambiguous wording, doc misinterpretation, or implementation details, I would recommend users refer to doc/policy/mempool-replacements.md
      - the signaling policy is configurable, see #25353
  - Our RBF policy may change further
  - We have already marked BIP125 as only "partially implemented" in docs/bips.md since 1fd49eb498c75a1d14193bb736d195a3dc75ae12
  - See comments from people who are not me recently:
      - https://github.com/bitcoin/bitcoin/pull/25038#discussion_r909507429
      - https://github.com/bitcoin/bitcoin/pull/25575#issuecomment-1179519204

  This PR removes all non-signaling mentions of BIP125 (if people feel strongly, we can remove all mentions of BIP125 period). It may be useful to refer to the concept of "tx opts in to RBF if it has at least one nSequence less than (0xffffffff - 1)" as "BIP125 signaling" because:
  - It is succint.
  - It has already been widely marketed as BIP125 opt-in signaling.
  - Our API uses it when referring to signaling (e.g. getmempoolentry["bip125-replaceable"] and wallet error message "not BIP 125 replaceable"). Changing those is more invasive.
  - If/when we have other ways to signal in the future, we can disambiguate them this way. See #25038 which proposes another way of signaling, and where I pulled these commits from.

  Alternatives:
  - Changing our policy to match BIP125. This doesn't make sense as, for example, we would have to remove the requirement that a replacement tx has a higher feerate (Rule 6).
  - Changing BIP125 to match what we have. This doesn't make sense as it would be a significant change to a BIP years after it was finalized and already used as a spec to implement RBF in other places.
  - Document our policy as a new BIP and give it a number. This might make sense if we don't expect things to change a lot, and can be done as a next step.

ACKs for top commit:
  darosior:
    ACK 1dc03dda05e9dce128e57f05bb7b1bb02b3cfb9e
  ariard:
    ACK 1dc03dda
  t-bast:
    ACK https://github.com/bitcoin/bitcoin/commit/1dc03dda05e9dce128e57f05bb7b1bb02b3cfb9e

Tree-SHA512: a3adc2039ec5785892d230ec442e50f47f7062717392728152bbbe27ce1c564141f85253143f53cb44e1331cf47476d74f5d2f4b3cd873fc3433d7a0aa783e02

3 files changed, 6 insertions, 6 deletions

diff --git a/src/wallet/feebumper.cpp b/src/wallet/feebumper.cpp
index 1d741cda6e..6d7bb299cc 100644
--- a/src/wallet/feebumper.cpp
+++ b/src/wallet/feebumper.cpp
@@ -128,8 +128,8 @@ static CFeeRate EstimateFeeRate(const CWallet& wallet, const CWalletTx& wtx, con
     // WALLET_INCREMENTAL_RELAY_FEE value to future proof against changes to
     // network wide policy for incremental relay fee that our node may not be
     // aware of. This ensures we're over the required relay fee rate
-    // (BIP 125 rule 4).  The replacement tx will be at least as large as the
-    // original tx, so the total fee will be greater (BIP 125 rule 3)
+    // (Rule 4).  The replacement tx will be at least as large as the
+    // original tx, so the total fee will be greater (Rule 3)
     CFeeRate node_incremental_relay_fee = wallet.chain().relayIncrementalFee();
     CFeeRate wallet_incremental_relay_fee = CFeeRate(WALLET_INCREMENTAL_RELAY_FEE);
     feerate += std::max(node_incremental_relay_fee, wallet_incremental_relay_fee);
diff --git a/src/wallet/rpc/spend.cpp b/src/wallet/rpc/spend.cpp
index 66adc1d327..92ab8cd085 100644
--- a/src/wallet/rpc/spend.cpp
+++ b/src/wallet/rpc/spend.cpp
@@ -224,7 +224,7 @@ RPCHelpMan sendtoaddress()
                                          "transaction, just kept in your wallet."},
                     {"subtractfeefromamount", RPCArg::Type::BOOL, RPCArg::Default{false}, "The fee will be deducted from the amount being sent.\n"
                                          "The recipient will receive less bitcoins than you enter in the amount field."},
-                    {"replaceable", RPCArg::Type::BOOL, RPCArg::DefaultHint{"wallet default"}, "Allow this transaction to be replaced by a transaction with higher fees via BIP 125"},
+                    {"replaceable", RPCArg::Type::BOOL, RPCArg::DefaultHint{"wallet default"}, "Signal that this transaction can replaced by a transaction (BIP 125)"},
                     {"conf_target", RPCArg::Type::NUM, RPCArg::DefaultHint{"wallet -txconfirmtarget"}, "Confirmation target in blocks"},
                     {"estimate_mode", RPCArg::Type::STR, RPCArg::Default{"unset"}, "The fee estimate mode, must be one of (case insensitive):\n"
                      "\"" + FeeModes("\"\n\"") + "\""},
@@ -333,7 +333,7 @@ RPCHelpMan sendmany()
                             {"address", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "Subtract fee from this address"},
                         },
                     },
-                    {"replaceable", RPCArg::Type::BOOL, RPCArg::DefaultHint{"wallet default"}, "Allow this transaction to be replaced by a transaction with higher fees via BIP 125"},
+                    {"replaceable", RPCArg::Type::BOOL, RPCArg::DefaultHint{"wallet default"}, "Signal that this transaction can replaced by a transaction (BIP 125)"},
                     {"conf_target", RPCArg::Type::NUM, RPCArg::DefaultHint{"wallet -txconfirmtarget"}, "Confirmation target in blocks"},
                     {"estimate_mode", RPCArg::Type::STR, RPCArg::Default{"unset"}, "The fee estimate mode, must be one of (case insensitive):\n"
                      "\"" + FeeModes("\"\n\"") + "\""},
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 934811dee1..9281045c21 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -93,7 +93,7 @@ static const CAmount DEFAULT_CONSOLIDATE_FEERATE{10000}; // 10 sat/vbyte
 static const CAmount DEFAULT_MAX_AVOIDPARTIALSPEND_FEE = 0;
 //! discourage APS fee higher than this amount
 constexpr CAmount HIGH_APS_FEE{COIN / 10000};
-//! minimum recommended increment for BIP 125 replacement txs
+//! minimum recommended increment for replacement txs
 static const CAmount WALLET_INCREMENTAL_RELAY_FEE = 5000;
 //! Default for -spendzeroconfchange
 static const bool DEFAULT_SPEND_ZEROCONF_CHANGE = true;
@@ -768,7 +768,7 @@ public:
     /* Mark a transaction (and it in-wallet descendants) as abandoned so its inputs may be respent. */
     bool AbandonTransaction(const uint256& hashTx);
 
-    /** Mark a transaction as replaced by another transaction (e.g., BIP 125). */
+    /** Mark a transaction as replaced by another transaction. */
     bool MarkReplaced(const uint256& originalHash, const uint256& newHash);
 
     /* Initializes the wallet, returns a new CWallet instance or a null pointer in case of an error */