title: maven, how to skip downloading artifact if already downloaded
body: <p>When my project builds, I see it keep hitting the some external repos to download artifacts, but it already did that just a few minutes ago in another build, and the artifacts are in my .m2 folder. How to set  the configuration: only download once (because the rule is that once an artifact is released, it's not updated right? only when I change the version should maven download a new one).</p>