RPC: add getbestblockhash, to return tip of best chain

src/bitcoinrpc.cpp

@@ -195,6 +195,7 @@ static const CRPCCommand vRPCCommands[] =
     { "help",                   &help,                   true,      true },
     { "stop",                   &stop,                   true,      true },
     { "getblockcount",          &getblockcount,          true,      false },
+    { "getbestblockhash",       &getbestblockhash,       true,      false },
     { "getconnectioncount",     &getconnectioncount,     true,      false },
     { "getpeerinfo",            &getpeerinfo,            true,      false },
     { "addnode",                &addnode,                true,      true },

src/bitcoinrpc.h

@@ -201,6 +201,7 @@ extern json_spirit::Value signrawtransaction(const json_spirit::Array& params, b
 extern json_spirit::Value sendrawtransaction(const json_spirit::Array& params, bool fHelp);
 
 extern json_spirit::Value getblockcount(const json_spirit::Array& params, bool fHelp); // in rpcblockchain.cpp
+extern json_spirit::Value getbestblockhash(const json_spirit::Array& params, bool fHelp);
 extern json_spirit::Value getdifficulty(const json_spirit::Array& params, bool fHelp);
 extern json_spirit::Value settxfee(const json_spirit::Array& params, bool fHelp);
 extern json_spirit::Value getrawmempool(const json_spirit::Array& params, bool fHelp);

src/rpcblockchain.cpp

@@ -82,6 +82,15 @@ Value getblockcount(const Array& params, bool fHelp)
     return nBestHeight;
 }
 
+Value getbestblockhash(const Array& params, bool fHelp)
+{
+    if (fHelp || params.size() != 0)
+        throw runtime_error(
+            "getbestblockhash\n"
+            "Returns the hash of the best (tip) block in the longest block chain.");
+
+    return hashBestChain.GetHex();
+}
 
 Value getdifficulty(const Array& params, bool fHelp)
 {