How to automatically build from the latest git tag?

I’m making a package for a Linux distro. I want the package not having to compile the code, but take the precompiled code from an Open Build Service project. So any package modification can be tested without having to compile.

The question is how to setup that project in order for it to be able to always build from the latest tag on git, and trigger a new build every time that tag is updated?

If that’s even possible. Thanks in advance.