If you prefer to host your code on GitHub, it is fine! You can use GitLab CI/CD the way that you host your code on GitHub, but build, test and deploy from GitLab. Take a look at https://about.gitlab.com/solutions/github/!
This is not a full standalone mode, because GitLab CI is a built-in solution that can not be easily separated, but might work for you.
We do not have immediate plans to ship that yet, but I pinged our product team member there. However we do have plans to ship multi-project pipeline with an "inversion of control".
You will be able to specify pipeline relation with an upstream project, and when someone pushes a commit to it, a downstream pipeline is going to be trigger automatically. See an issue about cross-project dependencies - https://gitlab.com/gitlab-org/gitlab-ee/issues/1681!
Thanks for this feedback! At GitLab, we believe that work is never done, and we are always looking for things we can improve, in our CI solution as well! Let me address some of your concerns:
1. There is only one pipeline allowed at the moment (see issue about support for multiple pipelines: https://gitlab.com/gitlab-org/gitlab-ce/issues/22972), but you can use multiple builds / stages to usually achieve the same. We also plan to add ability to control status using exist code from the build (see https://gitlab.com/gitlab-org/gitlab-ce/issues/25738). You can also use our pipeline trigger API with environment variables to control what get executed.
2. That is true, we already did some backstage work to improve that. In the meantime it is possible to explicitly depend on builds from the previous stages to download all artifacts in subsequent jobs.
3. I'm not sure if I understand correctly, what you want to accomplish, but if `[ci skip]` is not enough, then status based on the exit code may be helpful as well.
Recently we added a feature that makes it possible to trigger a new pipeline from UI. It can solve your problem. We are also working on extending our support for environments, so if you need a more flexible solution, stay tuned!
I'm developer who works with PHP for more than 12 years so far, and with Ruby/RoR for more than 2 years.
I would suggest you to stick to PHP to gain some experience, because Ruby/RoR programming requires some experience in order to not screw things up.
But Ruby gives you much more possibilities, however if you don't have experience and don't know what is best practice you can create a lot of junk code and chaos leading to serious problems (like your apps performance).
This is not a full standalone mode, because GitLab CI is a built-in solution that can not be easily separated, but might work for you.