[improve][misc] Enable rebase and merge to handle one PR of multiple semantic commits

[tisonkun]

For example #20321.

Most of the time we use squash and merge, but rebase and merge help sometimes to keep commits separate while reviewing them at once.

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository:

[michaeljmarshall]

It might help to provide committers with documentation on when to use which button. We haven't had the option previously, so this might confuse some. I hope we don't get any committers arguing for a force push update to master to change the history because they hit the wrong button.

[tisonkun]

OK. Let me start a mail thread first.

For documentation, I don't think committers read comments in .asf.yaml so probably a page under https://pulsar.apache.org/contribute/develop-coding-conventions/ said "Reviewing Pull Request" or "Merging Pull Request".

[michaeljmarshall]

Thanks @tisonkun. I agree with putting it in that section. A committer guide would be valuable--I don't think we have one though.