add autoprune information to RPC "getblockchaininfo"

src/rpcblockchain.cpp

@@ -492,6 +492,15 @@ Value getblockchaininfo(const Array& params, bool fHelp)
     obj.push_back(Pair("difficulty",            (double)GetDifficulty()));
     obj.push_back(Pair("verificationprogress",  Checkpoints::GuessVerificationProgress(chainActive.Tip())));
     obj.push_back(Pair("chainwork",             chainActive.Tip()->nChainWork.GetHex()));
+    obj.push_back(Pair("pruned",                fPruneMode));
+    if (fPruneMode)
+    {
+        CBlockIndex *block = chainActive.Tip();
+        while (block && block->pprev && (block->pprev->nStatus & BLOCK_HAVE_DATA))
+            block = block->pprev;
+
+        obj.push_back(Pair("pruneheight",        block->nHeight));
+    }
     return obj;
 }