* Huge reduction in memory use (2/3 or so on large nix-env -qas

operations): share ATermMaps between DrvInfos.

src/nix-env/main.cc

@@ -348,6 +348,7 @@ static void queryInstSources(EvalState & state,
                 assertStorePath(*i);
 
                 DrvInfo elem;
+                elem.attrs = shared_ptr<ATermMap>(new ATermMap()); /* ugh... */
                 string name = baseNameOf(*i);
                 unsigned int dash = name.find('-');
                 if (dash != string::npos)