It's implemented as a set of patches + new files for net new files I add myself, then to build it, the firefox source is downloaded and patched automatically -

It's implemented as a set of patches + new files for net new files I add myself, then to build it, the firefox source is downloaded and patched automatically - so bumping the underlying firefox version is generally very easy. I'm currently actually tracking the firefox beta channel because the frequent small updates are so easy to do.