refs.c: add refs_ref_exists()

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -241,9 +241,14 @@ int read_ref(const char *refname, struct object_id *oid)
 	return read_ref_full(refname, RESOLVE_REF_READING, oid, NULL);
 }
 
+static int refs_ref_exists(struct ref_store *refs, const char *refname)
+{
+	return !!refs_resolve_ref_unsafe(refs, refname, RESOLVE_REF_READING, NULL, NULL);
+}
+
 int ref_exists(const char *refname)
 {
-	return !!resolve_ref_unsafe(refname, RESOLVE_REF_READING, NULL, NULL);
+	return refs_ref_exists(get_main_ref_store(the_repository), refname);
 }
 
 static int match_ref_pattern(const char *refname,