Update readme script to handle local includes

docs/src/main/ruby/generate_readme.sh

@@ -16,9 +16,16 @@ end
 
 file = ARGV[0] if ARGV.length>0
 
-srcDir = File.dirname(file)
-out = "// Do not edit this file (e.g. go instead to docs/src/main/asciidoc)\n\n"
-doc = Asciidoctor.load_file file, safe: :safe, parse: false, attributes: 'allow-uri-read'
+# Copied from https://github.com/asciidoctor/asciidoctor-extensions-lab/blob/master/scripts/asciidoc-coalescer.rb
+doc = Asciidoctor.load_file file, safe: :unsafe, header_only: true, attributes: options[:attributes]
+header_attr_names = (doc.instance_variable_get :@attributes_modified).to_a
+header_attr_names.each {|k| doc.attributes[%(#{k}!)] = '' unless doc.attr? k }
+attrs = doc.attributes
+attrs['allow-uri-read'] = true
+puts attrs
+
+out = "// Do not edit this file (e.g. go instead to src/main/asciidoc)\n\n"
+doc = Asciidoctor.load_file file, safe: :unsafe, parse: false, attributes: attrs
 out << doc.reader.read
 
 unless options[:to_file]