From e1af71c24965bc087877d424a1828ac74ba2f6a4 Mon Sep 17 00:00:00 2001
From: Hashim1999164 <64767361+Hashim1999164@users.noreply.github.com>
Date: Wed, 19 Aug 2026 00:59:26 +0500
Subject: [PATCH] Match markup file extensions without regard to case.

---
 lib/github/markup/implementation.rb | 5 ++++-
 test/coverage_test.rb               | 2 ++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/github/markup/implementation.rb b/lib/github/markup/implementation.rb
index 458ab0d8..5e5c4aab 100644
--- a/lib/github/markup/implementation.rb
+++ b/lib/github/markup/implementation.rb
@@ -35,7 +35,10 @@ def match?(filename, language)
       private
 
       def file_ext_regexp
-        @file_ext_regexp ||= /\.(#{regexp})\z/
+        # Use regexp.source so an /i flag on this pattern applies to the
+        # extension itself. Interpolating a Regexp object embeds (?-mix:),
+        # which would keep .MD from matching /md/.
+        @file_ext_regexp ||= /\.(?:#{regexp.source})\z/i
       end
     end
   end
diff --git a/test/coverage_test.rb b/test/coverage_test.rb
index f5043b5d..63c27c8f 100644
--- a/test/coverage_test.rb
+++ b/test/coverage_test.rb
@@ -115,6 +115,8 @@ def initialize; super(/md|markdown/, []); end
       assert impl.match?("README.md", nil)
       # call again to cover the memoization branch in file_ext_regexp
       assert impl.match?("README.markdown", nil)
+      assert impl.match?("README.MD", nil)
+      assert impl.match?("README.Markdown", nil)
       refute impl.match?("README.txt", nil)
     end
   end