How do I find the latest version of an artifact from a maven repository

You can use the Maven Dependency Plugin goal get together with LATEST as version for your artifact:

mvn org.apache.maven.plugins:maven-dependency-plugin:2.8:get
    -DremoteRepositories=<URL_to_your_maven_repo>
    -Dartifact=<group_id>:<artifact_id>:LATEST
    -Dpackaging=jar
    -Ddest=<target_dir>/<artifact_name>.jar