t/helper: merge test-scrap-cache-tree into test-tool

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/helper/test-scrap-cache-tree.c

@@ -1,3 +1,4 @@
+#include "test-tool.h"
 #include "cache.h"
 #include "lockfile.h"
 #include "tree.h"
@@ -5,7 +6,7 @@
 
 static struct lock_file index_lock;
 
-int cmd_main(int ac, const char **av)
+int cmd__scrap_cache_tree(int ac, const char **av)
 {
 	setup_git_directory();
 	hold_locked_index(&index_lock, LOCK_DIE_ON_ERROR);