copy.h: move declarations for copy.c functions from cache.h

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/convert.c b/convert.c
index 5a2ea53..7cf7bd0 100644
--- a/convert.c
+++ b/convert.c
@@ -2,6 +2,7 @@
 #include "advice.h"
 #include "config.h"
 #include "convert.h"
+#include "copy.h"
 #include "gettext.h"
 #include "hex.h"
 #include "object-store.h"