setup.h: move declarations for setup.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/refs/files-backend.c b/refs/files-backend.c
index 0c3138e..d2b8925 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -14,6 +14,7 @@
 #include "../object.h"
 #include "../dir.h"
 #include "../chdir-notify.h"
+#include "../setup.h"
 #include "../worktree.h"
 #include "../wrapper.h"