Add corner case tests for diff-index and diff-files

diff --git a/tag.c b/tag.c
index d19f56d60cb166600f9fe906a213f20a04afe22e..4470d2bf78e1fbb00d00e487f41daa4373cf48e1 100644 (file)
--- a/tag.c
+++ b/tag.c
@@ -9,7 +9,10 @@ const char *tag_type = "tag";
 struct object *deref_tag(struct object *o, const char *warn, int warnlen)
 {
        while (o && o->type == OBJ_TAG)
-               o = parse_object(((struct tag *)o)->tagged->sha1);
+               if (((struct tag *)o)->tagged)
+                       o = parse_object(((struct tag *)o)->tagged->sha1);
+               else
+                       o = NULL;
        if (!o && warn) {
                if (!warnlen)
                        warnlen = strlen(warn);