ajout référence ver source

public/service-hydra-core.nix

@@ -7,6 +7,7 @@ let
   profiles = config.r6d.profiles;
 
 
+  #### https://github.com/NixOS/hydra/issues/413
   # Note that we use 'import <nixpkgs> {}' instead of 'pkgs'.
   # If we use the latter we get an infinite recursion
   # because we include hydra-src in the module imports below which in turn defines the 'pkgs' value.