fix(__internal) : fix slash problem in oldfiles (#3260)

* fix(__internal) : fix slash problem in oldfiles

- Problems

Problem with slash and backslash being mixed up is chronic issue of
neovim in Windows. it makes telescope prompt perceive same path
differently when it execute to oldfiles picker.

some function like `nvim_buf_get_name()` or `vim.v.oldfiles` give paths
which are mixed up with slash and backslash.

- What it did
For windows, it always needs to change slash(/) to backslash(\) when
function which deal with path because entry_maker works properly only
the case that path string has \ not /.

- Effect

1) oldfiles picker doesn't show duplicated list
2) `defaults.path_display` configuration feature will works well at
   oldfiles pikcer

* fix(__internal) : Repeated comments are erased

lua/telescope/builtin/__internal.lua

@@ -532,12 +532,19 @@ internal.oldfiles = function(opts)
   local current_file = vim.api.nvim_buf_get_name(current_buffer)
   local results = {}
 
+  if utils.iswin then -- for slash problem in windows
+    current_file = current_file:gsub("/", "\\")
+  end
+
   if opts.include_current_session then
     for _, buffer in ipairs(utils.split_lines(vim.fn.execute ":buffers! t")) do
       local match = tonumber(string.match(buffer, "%s*(%d+)"))
       local open_by_lsp = string.match(buffer, "line 0$")
       if match and not open_by_lsp then
         local file = vim.api.nvim_buf_get_name(match)
+        if utils.iswin then
+          file = file:gsub("/", "\\")
+        end
         if vim.loop.fs_stat(file) and match ~= current_buffer then
           table.insert(results, file)
         end
@@ -546,6 +553,9 @@ internal.oldfiles = function(opts)
   end
 
   for _, file in ipairs(vim.v.oldfiles) do
+    if utils.iswin then
+      file = file:gsub("/", "\\")
+    end
     local file_stat = vim.loop.fs_stat(file)
     if file_stat and file_stat.type == "file" and not vim.tbl_contains(results, file) and file ~= current_file then
       table.insert(results, file)