Contributor overview


b4 prep, b4 send and b4 trailers are available starting with version 0.10.

Even though b4 started out as a tool to help maintainers, beginning with the version 0.10 there is also a set of features aimed at making it easier for contributors to submit patch series:

  • b4 prep allows to get your patch series ready for sending to the maintainer for review

  • b4 send simplifies the process of submitting your patches to the upstream maintainer even if you don’t have access to a compliant SMTP server

  • b4 trailers simplifies the process of retrieving code-review trailers received on the distribution lists and applying them to your tree


This is a fairly new set of features and can still be buggy or do something unexpected. While a lot of work has gone into making sure that your git tree isn’t harmed in any way, it’s best to have backups and to always review things with --dry-run when that option is available.

If you come across a bug or unexpected behaviour, please report the problem to the Tools mailing list.

Is it still required to be able to send email?

While b4 send makes it possible to submit patches without having access to an SMTP server, you still need a reasonable mail server for participating in conversations and code review.

The main benefit of b4 send is that you no longer have to really care if your mail server performs some kind of content mangling that causes patches to become corrupted, or if it doesn’t provide a way to send mail via SMTP.

What’s the b4 contributor workflow?

You can expect to be working with git commits, so you should be familiar with such git commands as git commit --amend and git rebase -i. In general, the process goes like this:

  1. Prepare your patch series by using b4 prep and queueing your commits. Use git rebase -i to arrange the commits in the right order and to write good commit messages.

  2. Prepare your cover letter using b4 prep --edit-cover. You should provide a good overview of what your series does and why you think it will improve the current code.

  3. When you are almost ready to send, use b4 prep --auto-to-cc to collect the relevant addresses from your commits. If your project uses a MAINTAINERS file, this should also perform the required query to figure out whom to include on your patch series submission.

  4. Review the list of addresses that b4 added to the cover letter and, if you know what you’re doing, remove any that you think are unnecessary.

  5. Run pre-flight checks on your series to improve your chances of getting positive reviews.

  6. Send your series using b4 send. This should automatically increment your series to the next version and add changelog entries to the cover letter.

  7. Await code review and feedback from maintainers.

  8. Apply any received code-review trailers using b4 trailers -u.

  9. Use git rebase -i to make any changes to the code based on the feedback you receive. Remember to record these changes in the cover letter’s changelog.

  10. Unless maintainers accept your series and merge them upstream, go back to #2 and continue until you succeed.

  11. Clean up obsolete prep-managed branches using b4 prep --cleanup

Please read the rest of these docs for details on the prep, send, and trailers commands.