Subversion has a couple different ways it can represent deleted files,

and they're not always consistent. It's also changed throughout

Subversion development, meaning that our deleted file logic worked fine

on some versions, and less so on others, depending.
We weren't handling the case where a file was listed as deleted using a

destination revision of (nonexistent). We did handle this for the

source revision, and we handled Index: ... (deleted), but not this

version.
This change implements this support, checking for this revision

identifier and flagging the file as deleted. This only affects

newly-uploaded diffs.

Unit tests pass. Waiting on feedback from a user who reported the issue.