TwJSON.Import: add blockchain rescan warning

mmgen/proto/btc/tw/json.py

@@ -36,6 +36,16 @@ class BitcoinTwJSON(TwJSON):
 			few minutes.
 		"""
 
+		blockchain_rescan_warning = """
+			Balances have been updated in the new tracking wallet.  However, the wallet
+			is unaware of the used state of any spent addresses without balances, which
+			creates the danger of address reuse, especially when automatic change address
+			selection is in effect.
+
+			To avoid this danger and restore full tracking wallet functionality, rescan
+			the blockchain for used addresses by running ‘mmgen-tool rescan_blockchain’.
+		"""
+
 		@property
 		async def tracking_wallet_exists(self):
 			return await self.twctl.rpc.check_or_create_daemon_wallet(wallet_create=False)

mmgen/tw/json.py

@@ -62,6 +62,8 @@ class TwJSON:
 
 	class Import(Base,metaclass=AsyncInit):
 
+		blockchain_rescan_warning = None
+
 		async def __init__(self,proto,filename,ignore_checksum=False,batch=False):
 
 			super().__init__(proto)
@@ -104,6 +106,9 @@ class TwJSON:
 
 			await self.twctl.rescan_addresses(addrs)
 
+			if self.blockchain_rescan_warning:
+				ymsg('\n' + fmt(self.blockchain_rescan_warning.strip(),indent='  '))
+
 		async def check_and_create_wallet(self):
 
 			if await self.tracking_wallet_exists: