It is possible to add a "trash bin" feature to the CMS, which means that no document is ever deleted, it is simply filed under a different directory structure outside of the preview and live sites.

In order to use this, you need to do the following:

Add to build.properties:

cms.use.trash.bin=on

Re-initialise the repository if the following property is not set:

operation.createTrashLocationAndSetAcl=true