If the input begins with a slash, the resulting URL will be incorrect when the baseURL includes a subdirectory. With a leading slash, the function returns a URL relative to the protocol+host section of the baseURL.
As a result, the customJS and customCSS feature was broken when baseURL includes a subdirectory like https://example.com/blog.
Check https://gohugo.io/functions/relurl/#input-begins-with-a-slash for details.
As a result, the customJS and customCSS feature was broken when baseURL includes a subdirectory like
https://example.com/blog
.