Get head block number

- Allows us to refuse to sync past current head
- Creates the opportunity to add a flag for syncing all blocks

cmd/coldImport.go

@@ -49,10 +49,6 @@ func init() {
 }
 
 func coldImport() {
-	if endingBlockNumber < startingBlockNumber {
-		log.Fatal("Ending block number must be greater than starting block number for cold import.")
-	}
-
 	// init eth db
 	ethDBConfig := ethereum.CreateDatabaseConfig(ethereum.Level, levelDbPath)
 	ethDB, err := ethereum.CreateDatabase(ethDBConfig)
@@ -60,6 +56,14 @@ func coldImport() {
 		log.Fatal("Error connecting to ethereum db: ", err)
 	}
 
+	if endingBlockNumber < startingBlockNumber {
+		log.Fatal("Ending block number must be greater than starting block number for cold import.")
+	}
+	mostRecentBlockNumberInDb := ethDB.GetHeadBlockNumber()
+	if endingBlockNumber > mostRecentBlockNumberInDb {
+		log.Fatal("Ending block number is greater than most recent block in db: ", mostRecentBlockNumberInDb)
+	}
+
 	// init pg db
 	genesisBlockHash := common.BytesToHash(ethDB.GetBlockHash(0)).String()
 	coldNode := core.Node{