Sync bandwidth optimization

sync/src/blocks.rs

@@ -301,11 +301,16 @@ impl BlockCollection {
 		self.heads.len() == 0 || (self.heads.len() == 1 && self.head.map_or(false, |h| h == self.heads[0]))
 	}
 
-	/// Chech is collection contains a block header.
+	/// Check if collection contains a block header.
 	pub fn contains(&self, hash: &H256) -> bool {
 		self.blocks.contains_key(hash)
 	}
 
+	/// Check if collection contains a block header.
+	pub fn contains_head(&self, hash: &H256) -> bool {
+		self.heads.contains(hash)
+	}
+
 	/// Return used heap size.
 	pub fn heap_size(&self) -> usize {
 		self.heads.heap_size_of_children()