Add a new RPC command: restorewallet

[lsilva01]

As far as I know, there is no command to restore the wallet from a backup file.
The only way to do this is to replace the wallet.dat of a newly created wallet with the backup file, which is hardly an intuitive way.

This PR implements the restorewallet RPC command which restores the wallet from the backup file.

To test:
First create a backup file:
$ bitcoin-cli -rpcwallet="wallet-01" backupwallet /home/Backups/wallet-01.bak

Then restore it in another wallet:
$ bitcoin-cli restorewallet "restored-wallet-01" /home/Backups/wallet-01.bak

[ghost]

CI is failing because of whitespace at few places https://cirrus-ci.com/task/6700329929539584

You can automatically remove this pre commit by using "files.trimTrailingWhitespace": true in VS Code

[Rspigler]

Concept ACK!

[laanwj]

Concept ACK. I think this is more of an importwallet than restorewallet in the sense that an external wallet file is being imported into the data directory, which is slightly more general. But no strong opinion on RPC naming (ofc, importwallet already exists and does something else,).

The only way to do this is to replace the wallet.dat of a newly created wallet with the backup file, which is hardly an intuitive way.

I don't think the replacement part is necessary (or desirable). As I understand, you can place it in the wallets directory then do loadwallet.

Needs a RPC test.

[ghost]

As I understand, you can place it in the wallets directory then do loadwallet

This gives error:

$ bitcoin-cli loadwallet "B1.dat"

error code: -4
error message:
BerkeleyDatabase: Can't open database B1.dat (duplicates fileid b6050000000024007aceafe40000000000000000 from wallet.dat)

[S3RK]

@prayank23 the error says that you are trying to load a copy of already existing wallet. Try the same with the wallet created on another node

[ghost]

the error says that you are trying to load a copy of already existing wallet. Try the same with the wallet created on another node

Right. Wallet will be different when users restore from backup. Because if there is already a wallet, there is no need to restore.

Or it can be same in few cases?

[achow101]

Concept ACK

[lsilva01]

test/functional/wallet_backup.py has been changed to use the restorewallet command instead of manually inserting the files.
The original test stopped nodes before inserting them. As this is no longer necessary, the backup files are used to restore the wallets on the fourth node without restarting it.

[lsilva01]

5b0a506: Adds a helper function to load the wallet which is used by restorewallet and loadwallet.

8f87ef4: Increases coverage ofrestorewallet test. Adds restore_nonexistent_wallet and restore_wallet_existent_name functions.

[achow101]

ACK 8f87ef4

[achow101]

re-ACK 5fe8100

[DrahtBot]

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

Conflicts

Reviewers, this pull request conflicts with the following ones:

• #19101 (refactor: remove ::vpwallets and related global variables by ryanofsky)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

[meshcollider]

utACK 5fe8100

[ghost]

tACK 5fe8100

Tested on windows with below commands:

1. Create wallet W1:

   bitcoin-cli createwallet W1
   

2. Backup wallet:

   bitcoin-cli -rpcwallet="w1" backupwallet "D:\Backups\backup_W1.dat"
   

3. Delete wallet directory regtest\wallets\W1

4. Restore wallet from backup:

   bitcoin-cli restorewallet "W1" "D:\Backups\backup_W1.dat"
   

   {
    "name": "W1",
    "warning": ""
   }
   

5. Check wallet info: bitcoin-cli -rpcwallet="W1" getwalletinfo

[meshcollider]

Great first contribution, thank you! 🎉