The results from previous CI runs are no longer connected to the rebased commits, and most people don't have CI set up to retest each commit individually after a rebase.

I've never found this to be an actual problem in practice.

Since a rebase changes the commit sha, I assume that's used as a reference for which version of the code the CI test was run against.

That said, shouldn't CI be triggered after the rebase anyway to confirm all still works?

I see. But as you noted, one must do CI tests again after a rebase.

Indeed you need to do them again. But you also have to rerun them after a merge anyway. The problem is that you can no longer see which commits that you merged where green before the merge. For example is very useful if the merge itself breaks the tests (uncommon but it can happen).

Edit: There's a well-written solution for that here: https://news.ycombinator.com/item?id=9745367

Parent was deleted.

Ugh dammit. Short version:

Instead of taking the branch <feature> and rebasing it, make a branch called <feature>.1 on top of <feature>, then rebase that, leaving <feature> in place.

That way all your references remain intact and you can compare CI results.

Increment the number as needed.

It solves the issue of the CI references. But it also seems a bit clumsy to me.

It's all trade-offs. The trade-off being that you maintain history by having copies of a branch around, while the dude trying to fix a bug doesn't have to break out the vodka bottle upon arriving back home. :)

A CI test result is tied to a particular commit hash. If you change this commit hash the CI test result will no longer be tied to that one commit.