See last link for the details about the following highlights:
- Add security-updates command. A Composer equivalent for old --security-only option.(#3087)
- Better coding standards compliance for 'generate' command
- Better discovery of global commandfiles #3052
- Config for sql-sync options now properly proceessed #3075
- Check requirements before running updatedb #2708
- Control when post-updates are run during updatedb. (#3090)
- Misc bug fixes
- Changes since 9.0.0-beta7.