perf: get git status only once per refresh

autoload/magit/state.vim

@@ -277,8 +277,8 @@ function! magit#state#update() dict
 	try
 		call magit#utils#chdir(magit#git#top_dir())
 		call magit#utils#refresh_submodule_list()
-		for [mode, diff_dict_mode] in items(self.dict)
 		let status_list = magit#git#get_status()
+		for [mode, diff_dict_mode] in items(self.dict)
 			for file_status in status_list
 				let status=file_status[mode]