In a standard Upload (as derived from UploadBase), there is an mTempPath which represents where PHP was storing the tmpnam from its upload. When the paths are initialized, it may be set to be deleted once the file is copied to the Repo.
According to the current scheme, an UploadFromStash will configure things such that the stash file is the "temporary" file, and the same thing happens. Except it's configured to not be deleted. Why?
Also, since we let the Upload delete the file in an ordinary manner, the stash entries may persist after their files are deleted. This seems wrong too.
To fix this, we would have to get the main Upload object to invoke a delete method on UploadStash, rather than relying on the path of the UploadStash file being on the same machine, and being deletable. So that seems better for many reasons -- it's more abstract and has a better chance of working with other file stores than NFS.