Merge branch 'jc/refs-symref-referent'

The refs API has been taught to give symref target information to
the users of ref iterators, allowing for-each-ref and friends to
avoid an extra ref_resolve_* API call per a symbolic ref.

* jc/refs-symref-referent:
  ref-filter: populate symref from iterator
  refs: add referent to each_ref_fn
  refs: keep track of unresolved reference value in iterators

refs.h

@@ -298,7 +298,7 @@ struct ref_transaction;
  * arguments is only guaranteed to be valid for the duration of a
  * single callback invocation.
  */
-typedef int each_ref_fn(const char *refname,
+typedef int each_ref_fn(const char *refname, const char *referent,
 			const struct object_id *oid, int flags, void *cb_data);
 
 /*