runtime(gzip): load undofile if there exists one

fixes: #16102
closes: #16122

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/autoload/gzip.vim b/runtime/autoload/gzip.vim
index 26b1cda..a6fbe2c 100644
--- a/runtime/autoload/gzip.vim
+++ b/runtime/autoload/gzip.vim
@@ -1,6 +1,6 @@
 " Vim autoload file for editing compressed files.
 " Maintainer:	The Vim Project <https://github.com/vim/vim>
-" Last Change:	2023 Aug 10
+" Last Change:	2024 Nov 25
 " Former Maintainer: Bram Moolenaar <Bram@vim.org>
 
 " These functions are used by the gzip plugin.
@@ -148,6 +148,9 @@
     else
       let fname = escape(expand("%:r"), " \t\n*?[{`$\\%#'\"|!<")
     endif
+    if filereadable(undofile(expand("%")))
+      exe "sil rundo " . fnameescape(undofile(expand("%")))
+    endif
     if &verbose >= 8
       execute "doau BufReadPost " . fname
     else