core: Rework object iteration API to be GFile based and pass more data

It makes more sense to have e.g. the details of .packfile naming
inside the repo, and pass the expected checksum and type.

src/libostree/ostree-repo.h

@@ -157,13 +157,17 @@ gboolean      ostree_repo_diff (OstreeRepo     *self,
                                 GCancellable   *cancellable,
                                 GError        **error);
 
-typedef void (*OstreeRepoObjectIter) (OstreeRepo *self, const char *path,
-                                        GFileInfo *fileinfo, gpointer user_data);
+typedef void (*OstreeRepoObjectIter) (OstreeRepo *self, 
+                                      const char *checksum,
+                                      OstreeObjectType type,
+                                      GFile      *path,
+                                      GFileInfo  *fileinfo,
+                                      gpointer user_data);
 
 gboolean     ostree_repo_iter_objects (OstreeRepo  *self,
-                                         OstreeRepoObjectIter callback,
-                                         gpointer       user_data,
-                                         GError        **error);
+                                       OstreeRepoObjectIter callback,
+                                       gpointer       user_data,
+                                       GError        **error);
 
 G_END_DECLS