jenkins: promote before job ends
No, Promotions only run on completed builds. If you want to run it in the middle of the job, then it's a build step, not a promotion. You can either configure build steps for your actions (same actions as promotions). You can even call other jobs, and wait for them...
Legacy code started this job. No cause information is available
You probably have a post-commit hook that is triggering the same job through a URL or jenkins-cli Edit after OP comments: But I start to wonder on the deploy-job, I didnt configure "Build when a change is pushed to Github", instead, I use "Build when another project is promoted", so...