Manually escape '#' when building relative uris, fixes #42459

changelogs/unreleased/fix-42459---in-branch.yml

@@ -0,0 +1,5 @@
+---
+title: Fix relative uri when "#" is in branch name
+merge_request:
+author: Jan
+type: fixed

lib/banzai/filter/relative_link_filter.rb

@@ -84,7 +84,7 @@ module Banzai
           relative_url_root,
           project.full_path,
           uri_type(file_path),
-          Addressable::URI.escape(ref),
+          Addressable::URI.escape(ref).gsub('#', '%23'),
           Addressable::URI.escape(file_path)
         ].compact.join('/').squeeze('/').chomp('/')