Tell between packed, unpacked and symbolic refs.

This adds a "int *flag" parameter to resolve_ref() and makes
for_each_ref() family to call callback function with an extra
"int flag" parameter.  They are used to give two bits of
information (REF_ISSYMREF and REF_ISPACKED) about the ref.

Signed-off-by: Junio C Hamano <junkio@cox.net>

wt-status.c

@@ -41,7 +41,7 @@ void wt_status_prepare(struct wt_status *s)
 
 	s->is_initial = get_sha1("HEAD", sha1) ? 1 : 0;
 
-	head = resolve_ref("HEAD", sha1, 0);
+	head = resolve_ref("HEAD", sha1, 0, NULL);
 	s->branch = head ? xstrdup(head) : NULL;
 
 	s->reference = "HEAD";