refs: split off reading loose ref data in separate function

This prepares for handling FETCH_HEAD (which is not a regular ref)
separately from the ref backend.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs/refs-internal.h

@@ -674,6 +674,12 @@ struct ref_store {
 	const struct ref_storage_be *be;
 };
 
+/*
+ * Parse contents of a loose ref file.
+ */
+int parse_loose_ref_contents(const char *buf, struct object_id *oid,
+			     struct strbuf *referent, unsigned int *type);
+
 /*
  * Fill in the generic part of refs and add it to our collection of
  * reference stores.