refs: make create_symref() virtual

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/refs.c b/refs.c
index cdd78b9..312c766 100644
--- a/refs.c
+++ b/refs.c
@@ -1428,6 +1428,15 @@
 	return refs->be->pack_refs(refs, flags);
 }
 
+int create_symref(const char *ref_target, const char *refs_heads_master,
+		  const char *logmsg)
+{
+	struct ref_store *refs = get_ref_store(NULL);
+
+	return refs->be->create_symref(refs, ref_target, refs_heads_master,
+				       logmsg);
+}
+
 int ref_transaction_commit(struct ref_transaction *transaction,
 			   struct strbuf *err)
 {