sbt-native-packager: Append timestamp to version of Debian package for snapshots

build.sbt

version := "0.2-SNAPSHOT"

// If the version ends with "-SNAPSHOT", let the Debian version end with
// "~SNAPSHOT~yyyyMMddHHmmss". This way updates of the snapshot version can be
// detected by the package manager. Also the tilde "~" sorts before anything
// else when comparing version numbers. This way "1.0" will be regarded newer
// than "1.0~beta".
version in Debian <<= (version) { (v) =>
    if (v.endsWith("-SNAPSHOT")) {
       val timestampFormat = new java.text.SimpleDateFormat("yyyyMMddHHmmss");
       timestampFormat.setTimeZone(java.util.TimeZone.getTimeZone("UTC"));
       val now = timestampFormat.format(new java.util.Date());
       v.replace("-SNAPSHOT", "~SNAPSHOT~" + now)
    } else {
       v
    }
}