rpc: send confirmations in get_transactions result

if the wallet does it, it would get a wrong result (possibly even
negative) if its local chain is not synced up to the daemon's yet

src/rpc/core_rpc_server.cpp

@@ -1043,6 +1043,7 @@ namespace cryptonote
       if (e.in_pool)
       {
         e.block_height = e.block_timestamp = std::numeric_limits<uint64_t>::max();
+        e.confirmations = 0;
         auto it = per_tx_pool_tx_info.find(tx_hash);
         if (it != per_tx_pool_tx_info.end())
         {
@@ -1061,6 +1062,7 @@ namespace cryptonote
       else
       {
         e.block_height = m_core.get_blockchain_storage().get_db().get_tx_block_height(tx_hash);
+        e.confirmations = m_core.get_current_blockchain_height() - e.block_height;
         e.block_timestamp = m_core.get_blockchain_storage().get_db().get_block_timestamp(e.block_height);
         e.received_timestamp = 0;
         e.double_spend_seen = false;

src/rpc/core_rpc_server_commands_defs.h

@@ -88,7 +88,7 @@ namespace cryptonote
 // advance which version they will stop working with
 // Don't go over 32767 for any of these
 #define CORE_RPC_VERSION_MAJOR 3
-#define CORE_RPC_VERSION_MINOR 6
+#define CORE_RPC_VERSION_MINOR 7
 #define MAKE_CORE_RPC_VERSION(major,minor) (((major)<<16)|(minor))
 #define CORE_RPC_VERSION MAKE_CORE_RPC_VERSION(CORE_RPC_VERSION_MAJOR, CORE_RPC_VERSION_MINOR)
 
@@ -350,6 +350,7 @@ namespace cryptonote
       bool in_pool;
       bool double_spend_seen;
       uint64_t block_height;
+      uint64_t confirmations;
       uint64_t block_timestamp;
       uint64_t received_timestamp;
       std::vector<uint64_t> output_indices;
@@ -367,6 +368,7 @@ namespace cryptonote
         if (!this_ref.in_pool)
         {
           KV_SERIALIZE(block_height)
+          KV_SERIALIZE(confirmations)
           KV_SERIALIZE(block_timestamp)
           KV_SERIALIZE(output_indices)
         }

src/wallet/wallet2.cpp

@@ -11515,6 +11515,9 @@ void wallet2::check_tx_key_helper(const cryptonote::transaction &tx, const crypt
 
 void wallet2::check_tx_key_helper(const crypto::hash &txid, const crypto::key_derivation &derivation, const std::vector<crypto::key_derivation> &additional_derivations, const cryptonote::account_public_address &address, uint64_t &received, bool &in_pool, uint64_t &confirmations)
 {
+  uint32_t rpc_version;
+  THROW_WALLET_EXCEPTION_IF(!check_connection(&rpc_version), error::wallet_internal_error, "Failed to connect to daemon: " + get_daemon_address());
+
   COMMAND_RPC_GET_TRANSACTIONS::request req;
   COMMAND_RPC_GET_TRANSACTIONS::response res;
   req.txs_hashes.push_back(epee::string_tools::pod_to_hex(txid));
@@ -11559,12 +11562,19 @@ void wallet2::check_tx_key_helper(const crypto::hash &txid, const crypto::key_de
   in_pool = res.txs.front().in_pool;
   confirmations = 0;
   if (!in_pool)
+  {
+    if (rpc_version < MAKE_CORE_RPC_VERSION(3, 7))
     {
       std::string err;
       uint64_t bc_height = get_daemon_blockchain_height(err);
-    if (err.empty())
+      if (err.empty() && bc_height > res.txs.front().block_height)
         confirmations = bc_height - res.txs.front().block_height;
     }
+    else
+    {
+      confirmations = res.txs.front().confirmations;
+    }
+  }
 }
 
 std::string wallet2::get_tx_proof(const crypto::hash &txid, const cryptonote::account_public_address &address, bool is_subaddress, const std::string &message)