Do not treat bare multisig as IsMine

Such outputs can still be watched, and signed for, but they aren't treated as valid payments.
That means they won't cause transactions to appear in listtransactions, their outputs to be
shown under listunspent, or affect balances.

src/script/ismine.cpp

@@ -123,6 +123,9 @@ static isminetype IsMineInner(const CKeyStore& keystore, const CScript& scriptPu
 
     case TX_MULTISIG:
     {
+        // Never treat bare multisig outputs as ours (they can still be made watchonly-though)
+        if (sigversion == IsMineSigVersion::TOP) break;
+
         // Only consider transactions "mine" if we own ALL the
         // keys involved. Multi-signature transactions that are
         // partially owned (somebody else has a key that can spend

src/test/script_standard_tests.cpp

@@ -561,7 +561,14 @@ BOOST_AUTO_TEST_CASE(script_standard_IsMine)
         keystore.AddKey(keys[1]);
 
         result = IsMine(keystore, scriptPubKey, isInvalid);
-        BOOST_CHECK_EQUAL(result, ISMINE_SPENDABLE);
+        BOOST_CHECK_EQUAL(result, ISMINE_NO);
+        BOOST_CHECK(!isInvalid);
+
+        // Keystore has 2/2 keys and the script
+        keystore.AddCScript(scriptPubKey);
+
+        result = IsMine(keystore, scriptPubKey, isInvalid);
+        BOOST_CHECK_EQUAL(result, ISMINE_NO);
         BOOST_CHECK(!isInvalid);
     }
 

test/functional/feature_segwit.py

@@ -311,8 +311,10 @@ class SegWitTest(BitcoinTestFramework):
             v = self.nodes[0].getaddressinfo(i)
             if (v['isscript']):
                 [bare, p2sh, p2wsh, p2sh_p2wsh] = self.p2sh_address_to_script(v)
-                # bare and p2sh multisig with compressed keys should always be spendable
-                spendable_anytime.extend([bare, p2sh])
+                # p2sh multisig with compressed keys should always be spendable
+                spendable_anytime.extend([p2sh])
+                # bare multisig can be watched and signed, but is not treated as ours
+                solvable_after_importaddress.extend([bare])
                 # P2WSH and P2SH(P2WSH) multisig with compressed keys are spendable after direct importaddress
                 spendable_after_importaddress.extend([p2wsh, p2sh_p2wsh])
             else:
@@ -328,8 +330,10 @@ class SegWitTest(BitcoinTestFramework):
             v = self.nodes[0].getaddressinfo(i)
             if (v['isscript']):
                 [bare, p2sh, p2wsh, p2sh_p2wsh] = self.p2sh_address_to_script(v)
-                # bare and p2sh multisig with uncompressed keys should always be spendable
-                spendable_anytime.extend([bare, p2sh])
+                # p2sh multisig with uncompressed keys should always be spendable
+                spendable_anytime.extend([p2sh])
+                # bare multisig can be watched and signed, but is not treated as ours
+                solvable_after_importaddress.extend([bare])
                 # P2WSH and P2SH(P2WSH) multisig with uncompressed keys are never seen
                 unseen_anytime.extend([p2wsh, p2sh_p2wsh])
             else: