My experience is limited to GitHub Actions, GitLab CI, and Jenkins. I've never been in an organization that managed to crack the code on running Jenkins in a sane way (always a poorly maintained, bloated mess of plugins, unfortunately) so I can't say I count Jenkins as a contender in this conversation. One could argue it's unfair to discount Jenkins because of organizations that manage it poorly, but there's something to be said about a tool that is so easy to accidentally run in an unmaintainable way. I also have some limited experience with Drone and Circle, but not enough to talk about them confidently.
- Bring your own runner is easiest/most robust
- environment deploys and management
- tons of deployment integrations
- DevSecOps features
- Built in support ticket handling
- Free container & package registry
For most of these I’m pretty sure gitlab had them built into the platform (and free!) first
Of course GitHub came and blew that out of the water with a composable social actions ecosystem. Which was brilliant and remains the killer feature that puts GitHub far beyond reach of other CI platforms, especially now that they've improved in-repo composability a few months ago.
Out of those, I think only "composable workflow definitions" would be one of the features that other CI platforms didn't have, before GitLab even existed as a project. You might want to re-read the history and features of build platforms before GitLab.
As someone who only used GitLabs CI briefly when it initially launched, what hard parts did they innovate on exactly?
As far as I could tell, it's a run-of-the-mill CI/CD platform, for better or worse, but nothing I'd call "innovative".
But again, maybe since the first time I tried it when it launched, it has changed, and I missed something really cool they did.