[blockchain] Add latest-headers command to get chain headers (#206)

cmd/subcommands/blockchain.go

@@ -162,6 +162,13 @@ High level information about transaction, like blockNumber, blockHash
 			noLatest = true
 			return request(rpc.Method.GetLatestBlockHeader, []interface{}{})
 		},
+	}, {
+		Use:   "latest-headers",
+		Short: "Get the latest chain headers",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			noLatest = true
+			return request(rpc.Method.GetLatestChainHeaders, []interface{}{})
+		},
 	}, {
 		Use:   "resend-cx",
 		Short: "Re-play a cross shard transaction",

pkg/rpc/methods.go

@@ -70,6 +70,7 @@ type rpcEnumList struct {
 	GetCurrentBadBlocks                     method
 	GetShardID                              method
 	GetLastCrossLinks                       method
+	GetLatestChainHeaders                   method
 }
 
 // Method is a list of known RPC methods
@@ -132,6 +133,7 @@ var Method = rpcEnumList{
 	GetCurrentBadBlocks:                     "hmy_getCurrentBadBlocks",
 	GetShardID:                              "hmy_getShardID",
 	GetLastCrossLinks:                       "hmy_getLastCrossLinks",
+	GetLatestChainHeaders:                   "hmy_getLatestChainHeaders",
 }
 
 // TODO Use Reflection here to avoid typing out the cases