pack: move has_pack_index()

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/packfile.c b/packfile.c
index 322c43d..84d16bf 100644
--- a/packfile.c
+++ b/packfile.c
@@ -1846,3 +1846,11 @@ int has_sha1_pack(const unsigned char *sha1)
 	struct pack_entry e;
 	return find_pack_entry(sha1, &e);
 }
+
+int has_pack_index(const unsigned char *sha1)
+{
+	struct stat st;
+	if (stat(sha1_pack_index_name(sha1), &st))
+		return 0;
+	return 1;
+}