patch 9.1.1384: still some problem with the new tutors filetype plugin

Problem:  still some problem with the new tutors filetype plugin
Solution: refactor code to enable/disable tutor mode into
          tutor#EnableInteractive() function, include a test
          (Phạm Bình An)

I find it annoying that Tutor's interactive mode is always on (or debug
mode is off) even when I open a tutor file with :edit command.
I think it makes more sense to make this "interactive mode":

- Always on when it is opened with :Tutor command
- Off otherwise

For more references, see `:help` feature, it is a much better than
:Tutor, since I don't have to run `:let g:help_debug = 1` just to be able
to edit and save a help file

Therefore, I remove `g:tutor_debug`

closes: #17299

Signed-off-by: Phạm Bình An <phambinhanctb2004@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/Make_all.mak

@@ -245,6 +245,7 @@ NEW_TESTS = \
 	test_plugin_matchparen \
 	test_plugin_termdebug \
 	test_plugin_tohtml \
+	test_plugin_tutor \
 	test_plugin_zip \
 	test_plus_arg_edit \
 	test_popup \
@@ -511,6 +512,7 @@ NEW_TESTS_RES = \
 	test_plugin_matchparen.res \
 	test_plugin_termdebug.res \
 	test_plugin_tohtml.res \
+	test_plugin_tutor.res \
 	test_plugin_zip.res \
 	test_plus_arg_edit.res \
 	test_popup.res \

src/testdir/test_plugin_tutor.vim

@@ -0,0 +1,16 @@
+" Test for the new-tutor plugin
+
+func SetUp()
+  set nocompatible
+  runtime plugin/tutor.vim
+endfunc
+
+func Test_auto_enable_interactive()
+  Tutor
+  call assert_equal('nofile', &buftype)
+  call assert_match('tutor#EnableInteractive', b:undo_ftplugin)
+
+  edit Xtutor/Xtest.tutor
+  call assert_true(empty(&buftype))
+  call assert_match('tutor#EnableInteractive', b:undo_ftplugin)
+endfunc

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1384,
 /**/
     1383,
 /**/