How Play set up ivy repository?

Play sets ivy repository to ${PLAY_HOME}/repository instead of using the default Ivy home $HOME/.ivy2. Checkout the file ${PLAY_HOME}/play and you will find this at the end

"$JAVA" -Dsbt.ivy.home=$dir/repository -Dplay.home=$dir/framework -Dsbt.boot.properties=$dir/framework/sbt/play.boot.properties -jar $dir/framework/sbt/sbt-launch.jar "$@"

-Dsbt.ivy.home does the trick.