vim-patch:3704b5b: runtime(tutor): improve tutor.vim plugin and filetype plugin

- Set g:tutor_debug on startup if it doesn't exist so that users can get
  cmdline completion when interactively setting it.
- set b:undo_ftplugin in filetype plugin
- set default runtime file headers

closes: vim/vim#17274

3704b5b58a

Co-authored-by: Phạm Bình An <phambinhanctb2004@gmail.com>
(cherry picked from commit 238e1d6ecc)

runtime/ftplugin/tutor.vim

@@ -1,4 +1,11 @@
-" vim: fdm=marker
+" Tutor filetype plugin
+" Language:	Tutor (the new tutor plugin)
+" Maintainer:	This runtime file is looking for a new maintainer.
+" Last Change:	2025 May 10
+" Contributors:	Phạm Bình An <phambinhanctb2004@gmail.com>
+" Original Author: Felipe Morales <hel.sheep@gmail.com>
+" Last Change:
+" 2025 May 10 set b:undo_ftplugin
 
 " Base: {{{1
 call tutor#SetupVim()
@@ -43,3 +50,10 @@ if !exists('g:tutor_debug') || g:tutor_debug == 0
     call tutor#ApplyMarks()
     autocmd! TextChanged,TextChangedI <buffer> call tutor#ApplyMarksOnChanged()
 endif
+
+let b:undo_ftplugin = 'unlet! g:tutor_debug |'
+let b:undo_ftplugin ..= 'setl concealcursor< conceallevel< |'
+let b:undo_ftplugin ..= 'setl foldmethod< foldexpr< foldlevel< |'
+let b:undo_ftplugin ..= 'setl buftype< undofile< keywordprg< iskeyword< |'
+
+" vim: fdm=marker

runtime/plugin/tutor.vim

@@ -1,6 +1,17 @@
+" Tutor:	New Style Tutor Plugin :h vim-tutor-mode
+" Maintainer:	This runtime file is looking for a new maintainer.
+" Contributors:	Phạm Bình An <phambinhanctb2004@gmail.com>
+" Original Author: Felipe Morales <hel.sheep@gmail.com>
+" Date: 2025 May 10
+
 if exists('g:loaded_tutor_mode_plugin') || &compatible
     finish
 endif
 let g:loaded_tutor_mode_plugin = 1
 
+" Define this variable so that users get cmdline completion.
+if !exists('g:tutor_debug')
+  let g:tutor_debug = 0
+endif
+
 command! -nargs=? -complete=custom,tutor#TutorCmdComplete Tutor call tutor#TutorCmd(<q-args>)