Merge #16325: rpc: Clarify that block count means height excl genesis

fab0c820fa rpc: Clarify that block count means height excl genesis (MarcoFalke)

Pull request description:

  There is a common misconception that the block count returned by the blockchain rpcs includes the genesis block. See for example the discussion in https://github.com/bitcoin/bitcoin/pull/16292#issuecomment-506303256.

  However, it really returns the height, which is `0` for the genesis block.

  So clarify that and also remove the misleading "longest blockchain" comment.

  Finally, fix the wallet test that incorrectly used this rpc.

ACKs for top commit:
  instagibbs:
    utACK fab0c820fa
  promag:
    ACK fab0c82, sorry for the misconception.

Tree-SHA512: 0d087cbb628d3866352bca6420402f392e6a997e579941701a408a7fca355d84645045661f39b022e4479cc07f85a6cddaa9095b6fd9911b245692482420a5e4

src/rpc/blockchain.cpp

@@ -14,7 +14,6 @@
 #include <core_io.h>
 #include <hash.h>
 #include <index/blockfilterindex.h>
-#include <key_io.h>
 #include <policy/feerate.h>
 #include <policy/policy.h>
 #include <policy/rbf.h>
@@ -42,9 +41,9 @@
 
 #include <boost/thread/thread.hpp> // boost::thread::interrupt
 
+#include <condition_variable>
 #include <memory>
 #include <mutex>
-#include <condition_variable>
 
 struct CUpdatedBlock
 {
@@ -169,7 +168,8 @@ static UniValue getblockcount(const JSONRPCRequest& request)
     if (request.fHelp || request.params.size() != 0)
         throw std::runtime_error(
             RPCHelpMan{"getblockcount",
-                "\nReturns the number of blocks in the longest blockchain.\n",
+                "\nReturns the height of the most-work fully-validated chain.\n"
+                "The genesis block has height 0.\n",
                 {},
                 RPCResult{
             "n    (numeric) The current block count\n"
@@ -189,7 +189,7 @@ static UniValue getbestblockhash(const JSONRPCRequest& request)
     if (request.fHelp || request.params.size() != 0)
         throw std::runtime_error(
             RPCHelpMan{"getbestblockhash",
-                "\nReturns the hash of the best (tip) block in the longest blockchain.\n",
+                "\nReturns the hash of the best (tip) block in the most-work fully-validated chain.\n",
                 {},
                 RPCResult{
             "\"hex\"      (string) the block hash, hex-encoded\n"
@@ -1305,7 +1305,7 @@ UniValue getblockchaininfo(const JSONRPCRequest& request)
                 RPCResult{
             "{\n"
             "  \"chain\": \"xxxx\",              (string) current network name as defined in BIP70 (main, test, regtest)\n"
-            "  \"blocks\": xxxxxx,             (numeric) the current number of blocks processed in the server\n"
+            "  \"blocks\": xxxxxx,             (numeric) the height of the most-work fully-validated chain. The genesis block has height 0\n"
             "  \"headers\": xxxxxx,            (numeric) the current number of headers we have validated\n"
             "  \"bestblockhash\": \"...\",       (string) the hash of the currently best block\n"
             "  \"difficulty\": xxxxxx,         (numeric) the current difficulty\n"

test/functional/wallet_resendwallettransactions.py

@@ -57,8 +57,7 @@ class ResendWalletTransactionsTest(BitcoinTestFramework):
         # after the last time we tried to broadcast. Use mocktime and give an extra minute to be sure.
         block_time = int(time.time()) + 6 * 60
         node.setmocktime(block_time)
-        block = create_block(int(node.getbestblockhash(), 16), create_coinbase(node.getblockchaininfo()['blocks']), block_time)
-        block.nVersion = 3
+        block = create_block(int(node.getbestblockhash(), 16), create_coinbase(node.getblockcount() + 1), block_time)
         block.rehash()
         block.solve()
         node.submitblock(ToHex(block))