Jenkins

Jenkins is an open-source automation server for continuous integration and delivery. You describe a pipeline once, and from then on it runs the tests and pushes the deploys that someone would otherwise be babysitting by hand.

Integration happens through plugins, and there are hundreds of them, so connecting whatever build tools you already run is usually a matter of finding the right one rather than writing it. The flip side is that adopting Jenkins is largely an exercise in choosing plugins and wiring them together. That is where most of the setup time goes.