Add Note Locking to z_mergetoaddress
Adds note locking to `z_mergetoaddress` allowing it to be invoked multiple times before previous `z_mergetoaddress` operations have finished.
Reference issue [#3046](https://github.com/zcash/zcash/issues/3046)
Co-authored-by: Eirik Ogilvie-Wigley <eirik@z.cash>
Ignore -mempooltxinputlimit once Overwinter activates
Overwinter changes the SignatureHash function to solve the quadratic hashing problem, so this option will no longer be needed.
We do not need to be able to calculate multiple SignatureHash versions for a
single transaction format; instead, we use the transaction format to determine
the SigVersion.
The consensus branch ID *does* need to be passed in from the outside, as only
the caller knows the context in which the SignatureHash is being calculated
(ie. mempool acceptance vs. block validation).
JoinSplit signature verification has been moved into ContextualCheckTransaction,
where the consensus branch ID can be obtained.
The argument to the sign command for zcash-tx has been modified to take a height
in addition to the optional sigtype flags.
The wallet code previously assumed that an unlocked wallet would always
have a spending key associated with a note decryptor. Viewing keys break
this assumption.
For steady-state operation, this reduces the average time between wallet disk
writes from once per block to once per hour.
On -rescan, witness caches are only written out at the end along with the best
block, increasing speed while ensuring that on-disk state is kept consistent.
Witness caches are now never recreated during a -reindex, on the assumption that
the blocks themselves are not changing (the chain is just being reconstructed),
and so the witnesses will remain valid.
Part of #1749.
Return a more informative error message when trying to spend coinbase; select non-coinbase inputs when sending to a transparent output if needed
For #1373 and #1519
Code change:
- Extra parameter added to AvailableCoins to include or exclude Coinbase coins. Default value of parameter is 'true' as current behaviour is to include Coinbase coins.
- SelectCoins, used for sending taddr->taddr, will now exclude Coinbase coins.
Unit test:
Tried to write a test to focus on the extra parameter added to AvailableCoins but could not.
Empirical testing on Testnet:
Current behaviour is that upstream RPC commands sendfrom and sendtoaddress try to spend coinbase coins returned by AvailableCoins. So the user will see:
```
./zcash-cli sendtoaddress mrEGRmGJhmwAa4MQjzGd86ry63vrvovu9b 1000.0
error: {"code":-6,"message":"Insufficient funds"}
./zcash-cli sendtoaddress mrEGRmGJhmwAa4MQjzGd86ry63vrvovu9b 0.00003000
error: {"code":-4,"message":"Error: The transaction was rejected! This might happen if some of the coins in your wallet were already spent, such as if you used a copy of wallet.dat and coins were spent in the copy but not marked as spent here."}
./zcash-cli sendfrom "" mrEGRmGJhmwAa4MQjzGd86ry63vrvovu9b 0.00003000
error: {"code":-4,"message":"Error: The transaction was rejected! This might happen if some of the coins in your wallet were already spent, such as if you used a copy of wallet.dat and coins were spent in the copy but not marked as spent here."}
```
After fix is applied:
```
./zcash-cli sendtoaddress mrEGRmGJhmwAa4MQjzGd86ry63vrvovu9b 1000.0
error: {"code":-6,"message":"Insufficient funds"}
./zcash-cli sendtoaddress mrEGRmGJhmwAa4MQjzGd86ry63vrvovu9b 0.00003000
error: {"code":-4,"message":"Coinbase funds can only be sent to a zaddr"}
```
When non-coinbase UTXOs exist, they will now be selected and used:
```
./zcash-cli z_sendmany tnPJZHeVxegCg91utaquBRPEDBGjozfz9iLDHt7zvphFbZdspNgkTVLCGjDcadQBKNyUwKs8pNjDXuEZKrE1aNLpFwHgz4t '[{"address":"mx5fTRhLZwbYE7ZqhAPueZgQGSnwTbdvKU", "amount":0.01}]'
./zcash-cli sendtoaddress mrEGRmGJhmwAa4MQjzGd86ry63vrvovu9b 1000.0
error: {"code":-6,"message":"Insufficient funds"}
./zcash-cli sendtoaddress mrEGRmGJhmwAa4MQjzGd86ry63vrvovu9b 0.00003000
9818e543ac2f689d4ce8b52087607d73fecd771d45d316a1d9db092f0485aff2
./zcash-cli sendfrom "" mrEGRmGJhmwAa4MQjzGd86ry63vrvovu9b 0.00003000
899f2894823f51f15fc73b5e0871ac943edbe0ff88e1635f86906087b72caf30
```
Extra parameter added to AvailableCoins to include or exclude Coinbase coins.
SelectCoins, used for sending taddr->taddr, will exclude Coinbase coins.
Added qa rpc test and a runtime parameter -regtestprotectcoinbase to enforce
the coinbase->zaddr consensus rule in regtest mode.
