Merge #11687: External wallet files

be8ab7d08 Create new wallet databases as directories rather than files (Russell Yanofsky)
26c06f24e Allow wallet files not in -walletdir directory (Russell Yanofsky)
d8a99f65e Allow wallet files in multiple directories (Russell Yanofsky)

Pull request description:

  This change consists of three commits:

  * The first commit is a pure refactoring that removes the restriction that two wallets can only be opened at the same time if they are contained in the same directory.
  * The second commit removes the restriction that `-wallet` filenames can only refer to files in the `-walletdir` directory.
  * The third commit makes second commit a little safer by changing bitcoin to create wallet databases as directories rather than files, so they can be safely backed up.

  All three commits should be straightforward:

  *  The first commit adds around 20 lines of new code and then updates a bunch of function signatures (generally updating them to take plain fs::path parameters, instead of combinations of strings, fs::paths, and objects like CDBEnv and CWalletDBWrapper).
  * The second commit removes two `-wallet` filename checks and adds some test cases to the multiwallet unit test.
  * The third commit just changes the mapping from specified wallet paths to bdb environment & data paths.

    ---

  **Note:** For anybody looking at this PR for the first time, I think you can skip the comments before _20 Nov_ and start reading at https://github.com/bitcoin/bitcoin/pull/11687#issuecomment-345625565. Comments before  _20 Nov_ were about an earlier version of the PR that didn't include the third commit, and then confusion from not seeing the first commit.

Tree-SHA512: 00bbb120fe0df847cf57014f75f1f7f1f58b0b62fa0b3adab4560163ebdfe06ccdfff33b4231693f03c5dc23601cb41954a07bcea9a4919c8d42f7d62bcf6024

src/wallet/walletdb.cpp

@@ -771,16 +771,16 @@ void MaybeCompactWalletDB()
 //
 // Try to (very carefully!) recover wallet file if there is a problem.
 //
-bool CWalletDB::Recover(const std::string& filename, void *callbackDataIn, bool (*recoverKVcallback)(void* callbackData, CDataStream ssKey, CDataStream ssValue), std::string& out_backup_filename)
+bool CWalletDB::Recover(const fs::path& wallet_path, void *callbackDataIn, bool (*recoverKVcallback)(void* callbackData, CDataStream ssKey, CDataStream ssValue), std::string& out_backup_filename)
 {
-    return CDB::Recover(filename, callbackDataIn, recoverKVcallback, out_backup_filename);
+    return CDB::Recover(wallet_path, callbackDataIn, recoverKVcallback, out_backup_filename);
 }
 
-bool CWalletDB::Recover(const std::string& filename, std::string& out_backup_filename)
+bool CWalletDB::Recover(const fs::path& wallet_path, std::string& out_backup_filename)
 {
     // recover without a key filter callback
     // results in recovering all record types
-    return CWalletDB::Recover(filename, nullptr, nullptr, out_backup_filename);
+    return CWalletDB::Recover(wallet_path, nullptr, nullptr, out_backup_filename);
 }
 
 bool CWalletDB::RecoverKeysOnlyFilter(void *callbackData, CDataStream ssKey, CDataStream ssValue)
@@ -806,14 +806,14 @@ bool CWalletDB::RecoverKeysOnlyFilter(void *callbackData, CDataStream ssKey, CDa
     return true;
 }
 
-bool CWalletDB::VerifyEnvironment(const std::string& walletFile, const fs::path& walletDir, std::string& errorStr)
+bool CWalletDB::VerifyEnvironment(const fs::path& wallet_path, std::string& errorStr)
 {
-    return CDB::VerifyEnvironment(walletFile, walletDir, errorStr);
+    return CDB::VerifyEnvironment(wallet_path, errorStr);
 }
 
-bool CWalletDB::VerifyDatabaseFile(const std::string& walletFile, const fs::path& walletDir, std::string& warningStr, std::string& errorStr)
+bool CWalletDB::VerifyDatabaseFile(const fs::path& wallet_path, std::string& warningStr, std::string& errorStr)
 {
-    return CDB::VerifyDatabaseFile(walletFile, walletDir, warningStr, errorStr, CWalletDB::Recover);
+    return CDB::VerifyDatabaseFile(wallet_path, warningStr, errorStr, CWalletDB::Recover);
 }
 
 bool CWalletDB::WriteDestData(const std::string &address, const std::string &key, const std::string &value)