The server-config-defaults.txt file can be used to detect new configuration
options for the graylog2-server.
java -jar /path/to/graylog2-bootstrap/target/graylog2.jar server \
-f misc/graylog2.conf --dump-config | \
grep -v -e '^#' -e '^$' -e 'INFO : ' | \
sort -u > server-config.defaults'
Just diff the newly created file to see any changes to the default config.