ant tar task: way to enable "tar append"?

Goal: use ant to create a single tar archive for any combination of (say) 5 folders (all folders, or any 3 folders or any 4 folders ...). I prefer not using temp dirs and the copy command.

This should be simple if the ant tar task supports append.

A search lead me to:

Setting mode="update" in the compress antlib's tar task should do what is requ开发者_运维百科ested.

from: https://issues.apache.org/bugzilla/show_bug.cgi?id=39617

How do I know if 'antlib' is installed, or how do I install it. How does one set mode="update" - which file is chgd?.

-- What is the best way to enable "tar apend" in ant's tar task?

-- thanks