fix: user_index based sorting ( create index )

for performance, create index once,
using index to re-ordering

lua/nvim-tree/explorer/sorters.lua

@@ -83,32 +83,25 @@ function M.merge_sort(t, comparator)
 
     if type(user_order) == "table" then
       -- do merge sort for prevent memory exceed
+      local user_index = {}
+      for k, v in pairs(user_order) do
+        if user_index[v] == nil then
+          user_index[v] = k
+        end
+      end
       local mini_comparator = function(a, b)
-        local a_index = vim.tbl_indexof(user_order, a.absolute_path)
-        local b_index = vim.tbl_indexof(user_order, b.absolute_path)
-        if a_index == -1 then
+        local a_index = user_index[a.absolute_path]
+        local b_index = user_index[b.absolute_path]
+        if a_index == -1 or a_index == nil then
           a_index = 9999999999
         end
-        if b_index == -1 then
+        if b_index == -1 or a_index == nil then
           b_index = 9999999999
         end
         return a_index < b_index
       end
 
       split_merge(t, 1, #t, mini_comparator) -- sort by user order
-
-      -- for _, n in ipairs(user_order) do
-      --   for i = 1, #user_order, 1 do
-      --     for j = 1, #t, 1 do
-      --       if t[j] and t[j].absolute_path == user_order[i] then
-      --         local tmp = t[i]
-      --         t[i] = t[j]
-      --         t[j] = tmp
-      --         break
-      --       end
-      --     end
-      --   end -- reorder the list according to the user order
-      -- end
     end
   else
     if not comparator then