refacto: abstract TreeExplorer in core.lua

lua/nvim-tree/actions/dir-up.lua

@@ -1,4 +1,5 @@
 local utils = require "nvim-tree.utils"
+local core = require "nvim-tree.core"
 
 local M = {}
 
@@ -6,7 +7,7 @@ function M.fn(node)
   if not node or node.name == ".." then
     return require("nvim-tree.actions.change-dir").fn ".."
   else
-    local newdir = vim.fn.fnamemodify(utils.path_remove_trailing(TreeExplorer.cwd), ":h")
+    local newdir = vim.fn.fnamemodify(utils.path_remove_trailing(core.get_cwd()), ":h")
     require("nvim-tree.actions.change-dir").fn(newdir)
     return require("nvim-tree.actions.find-file").fn(node.absolute_path)
   end