revert: split between newly added file and file added in other changeset
These two kinds of files are handled differently. One is deleted and the other
is just forgotten (the file is untracked but left in place). The distinction is
done in the `_performrevert` code itself and we would like to get ride of this.
<?xml version="1.0" encoding="{encoding}"?>
<feed xmlns="http://www.w3.org/2005/Atom">