Correct GetBlockHashes chunk size after first phase

CHANGES.md

@@ -78,6 +78,7 @@ To be released.
     instead of the window size of a chunk (i.e., 500).  [[#396], [#399]]
  -  `Swarm<T>.PreloadAsync()` became to get the first parameter, `progress`,
     which accepts `IProgress<PreloadState>`.  [[#397], [#400]]
+ -  Response of `getBlockHashes()` now contains one more higher hash. [[#408]]
  -  `Swarm<T>.PreloadAsync()` became safe from data corruption even
     if a preloading process suddenly gets shutdown.  [[#417]]
  -  `FileStore` and `LiteDBStore` became to guarantee atomicity of storing
@@ -138,6 +139,7 @@ To be released.
 [#398]: https://github.com/planetarium/libplanet/pull/398
 [#399]: https://github.com/planetarium/libplanet/pull/399
 [#400]: https://github.com/planetarium/libplanet/pull/400
+[#408]: https://github.com/planetarium/libplanet/issues/408
 [#410]: https://github.com/planetarium/libplanet/issues/410
 [#413]: https://github.com/planetarium/libplanet/pull/413
 [#414]: https://github.com/planetarium/libplanet/pull/414

Libplanet/Blockchain/BlockChain.cs

@@ -770,6 +770,17 @@ internal IEnumerable<HashDigest<SHA256>> FindNextHashes(
 
                 HashDigest<SHA256> branchPoint = FindBranchPoint(locator);
                 var branchPointIndex = (int)Blocks[branchPoint].Index;
+
+                // FIXME: Currently, increasing count by one to satisfy
+                // the number defined by FindNextHashesChunkSize variable
+                // when branchPointIndex didn't indicate genesis block.
+                // Since branchPointIndex is same as the latest block of
+                // requesting peer.
+                if (branchPointIndex > 0)
+                {
+                    count++;
+                }
+
                 IEnumerable<HashDigest<SHA256>> hashes = Store
                     .IterateIndex(Id.ToString(), branchPointIndex, count);