runtime(java): Consent to HTML tags folding in Javadoc comments

HTML tags in Javadoc comments can additionally be folded
after applying
------------------------------------------------------------
	let g:html_syntax_folding = 1
	set foldmethod=syntax
------------------------------------------------------------

and giving explicit consent with
------------------------------------------------------------
	let g:java_consent_to_html_syntax_folding = 1
------------------------------------------------------------

Do not default to this kind of folding unless ALL start tags
and optional end tags are balanced in Javadoc comments;
otherwise, put up with creating runaway folds that break
syntax highlighting.

resolves: zzzyxwvut/java-vim#8.
closes: #17216

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/java.vim b/runtime/syntax/java.vim
index 8dabc5e..37b99b7 100644
--- a/runtime/syntax/java.vim
+++ b/runtime/syntax/java.vim
@@ -3,7 +3,7 @@
 " Maintainer:		Aliaksei Budavei <0x000c70 AT gmail DOT com>
 " Former Maintainer:	Claudio Fleiner <claudio@fleiner.com>
 " Repository:		https://github.com/zzzyxwvut/java-vim.git
-" Last Change:		2025 Mar 26
+" Last Change:		2025 Apr 28
 
 " Please check ":help java.vim" for comments on some of the options
 " available.
@@ -387,15 +387,30 @@
   " Include HTML syntax coloring for Javadoc comments.
   if s:with_html
     try
+      if exists("g:html_syntax_folding") && !exists("g:java_consent_to_html_syntax_folding")
+	let s:html_syntax_folding_copy = g:html_syntax_folding
+	unlet g:html_syntax_folding
+      endif
+
       syntax include @javaHtml syntax/html.vim
     finally
       unlet! b:current_syntax
+
+      if exists("s:html_syntax_folding_copy")
+	let g:html_syntax_folding = s:html_syntax_folding_copy
+	unlet s:html_syntax_folding_copy
+      endif
     endtry
   endif
 
   " Include Markdown syntax coloring (v7.2.437) for Javadoc comments.
   if s:with_markdown
     try
+      if exists("g:html_syntax_folding") && !exists("g:java_consent_to_html_syntax_folding")
+	let s:html_syntax_folding_copy = g:html_syntax_folding
+	unlet g:html_syntax_folding
+      endif
+
       syntax include @javaMarkdown syntax/markdown.vim
 
       try
@@ -413,6 +428,11 @@
     finally
       unlet! b:current_syntax
 
+      if exists("s:html_syntax_folding_copy")
+	let g:html_syntax_folding = s:html_syntax_folding_copy
+	unlet s:html_syntax_folding_copy
+      endif
+
       if exists("s:no_support")
 	unlet s:no_support
 	unlockvar s:with_markdown