* Store the size of a store path in the database (to be precise, the

size of the NAR serialisation of the path, i.e., `nix-store --dump
  PATH').  This is useful for Hydra.

src/libstore/references.hh

@@ -7,7 +7,7 @@
 namespace nix {
 
 PathSet scanForReferences(const Path & path, const PathSet & refs,
-    Hash & hash);
+    HashResult & hash);
     
 }