I've checked the mailing list archive and bugzilla and was surprised to find no discussion on adding compression options to the tar and untar tasks.
Currently to create a compressed tar file, you can use a <tar> task followed by a <gzip> or <bzip2> tasks. While that works, it requires sufficient disk space for the intermediate tar file which may be inconvenient when working for extremely large archives. It would seem to be fairly simple to add a compress attribute with acceptable values of "none", "gzip" and "bzip2" to the tar and untar tasks to enable them to create or expand tar.gz or tar.bz files in one step.
