Discuss get jars behavior

For get jars command add in #907 the command expects the target directory to exist but does not care if the directory is non-empty. I found myself wondering if the behavior should change or if the docs should be improved to clearly state the behavior for a non-empty dir while looking at the PR. I was not sure. Below are some thoughts I had.

* Should the get jars command create the dir?
* If the directory is not empty should the get jars command fail? Their are two use cases to consider.
* A user intentionally adds jars to a dir before calling get jars and does not expect it to empty.
* A user unintentionally reuses a dir and expects the dir to be empty when its not and ends ups extra/unexpected jars in the dir.

Start by reviewing the get jars command and the behavior discussed in #907. Decide whether it should create the target directory, reject non-empty directories, preserve existing contents, or document the current behavior; done means the chosen behavior is agreed and clearly specified.

Written by the indexing model from the issue text.