nvim: refine MY_get_project_root()

.config/nvim/lua/my/functions.lua

@@ -1,10 +1,8 @@
--- remove trailing whitespace
 function MY_remove_trailing_whitespace()
     local curpos = vim.api.nvim_win_get_cursor(0)
     vim.cmd([[keeppatterns %s/\s\+$//e]])
     vim.api.nvim_win_set_cursor(0, curpos)
 end
-
 vim.api.nvim_create_augroup('config_functions', { clear = true })
 vim.api.nvim_create_autocmd(
     { 'BufWritePre' },
@@ -91,7 +89,7 @@ function MY_get_project_root()
     local sep = '/'
 
     repeat
-        path = path:gsub('/[^/]*$', '')
+        path = path:gsub(string.format('%s[^%s]*$', sep, sep), '')
         for _, marker in ipairs(root_markers) do
             if io.open(path .. sep .. marker) then
                 return path