* New primop builtins.filterSource, which can be used to filter files

from a source directory.  All files for which a predicate function
  returns true are copied to the store.  Typical example is to leave
  out the .svn directory:

    stdenv.mkDerivation {
      ...
      src = builtins.filterSource
        (path: baseNameOf (toString path) != ".svn")
        ./source-dir;
      # as opposed to
      #   src = ./source-dir;
    }

  This is important because the .svn directory influences the hash in
  a rather unpredictable and variable way.

src/libutil/util.hh

@@ -164,10 +164,10 @@ struct AutoDeleteArray
 
 class AutoDelete
 {
-    string path;
+    Path path;
     bool del;
 public:
-    AutoDelete(const string & p);
+    AutoDelete(const Path & p);
     ~AutoDelete();
     void cancel();
 };