feat: allow passing a custom function as a window picker

WIP

Author: davidsierradz

lua/nvim-tree.lua

@@ -621,6 +621,7 @@ local DEFAULT_OPTS = { -- BEGIN_DEFAULT_OPTS
       resize_window = true,
       window_picker = {
         enable = true,
+        custom_function = nil,
         chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890",
         exclude = {
           filetype = { "notify", "packer", "qf", "diff", "fugitive", "fugitiveblame" },
@@ -672,6 +673,7 @@ end
 
 local FIELD_SKIP_VALIDATE = {
   open_win_config = true,
+  custom_function = true,
 }
 
 local FIELD_OVERRIDE_TYPECHECK = {

lua/nvim-tree/actions/node/open-file.lua

@@ -175,7 +175,7 @@ local function get_target_winid(mode, win_ids)
     end
   else
     -- pick a window
-    target_winid = pick_win_id()
+    target_winid = M.window_picker.custom_function and M.window_picker.custom_function() or pick_win_id()
     if target_winid == nil then
       -- pick failed/cancelled
       return