[Development] New features in CI

[Oswald Buddenhagen]

On Mon, Mar 01, 2021 at 01:25:50PM +0000, Lars Knoll wrote:
>First of all, you can now find a ‘Precheck' button in gerrit. That 
>button triggers a full CI test run of the Sha1 in the change and will 
>post back the result of that run as a comment.
>
so this simply exposes the pre-existing functionality. that means that 
testing a change accurately requires always rebasing it, which is 
exactly the opposite of the usual recommendation to not rebase unless 
conflicts occur. the system should instead create a build branch which 
is simply a rebase of the chosen sha1 (incl. its ancestors) to the tip 
of the target branch.

>If a staging branch passes, all the changes contained in that branch 
>will be merged into the target branch (can be a fast-forward merge).
>
you mean actual git merges, rather than rebases/cherry-picks? that will 
lead to a completely insane history in busy repositories.

>The one drawback is that we can in some rare cases end up with a 
>repository in a state where two staging branches passed CI and didn’t 
>conflict when merging them, but the merged state does not pass CI 
>anymore for some reason. 
>
if you accept that, there is no point in the custom CI gate in the first 
place - just assign a required review label to the CI system like almost 
every other project in the world does.

also, rather than sinking more and more resources into coin, you should 
have a look at zuul, which is a very gerrit-centric CI with a much 
better feature set and an actual community around it.