* modifies the reference also returns a nonzero value to immediately
* stop the iteration. Returned references are sorted.
*/
+int refs_head_ref(struct ref_store *refs,
+ each_ref_fn fn, void *cb_data);
int refs_for_each_ref(struct ref_store *refs,
each_ref_fn fn, void *cb_data);
int refs_for_each_ref_in(struct ref_store *refs, const char *prefix,