// preserveInTarget would find all files we want to keep,
// but we need to find all that we want to delete - so the
// meaning of all patterns and selectors must be inverted
PatternSet ps = syncTarget.mergePatterns(getProject());
fs.appendExcludes(ps.getIncludePatterns(getProject()));
fs.appendIncludes(ps.getExcludePatterns(getProject()));
fs.setDefaultexcludes(!syncTarget.getDefaultexcludes());
// selectors are implicitly ANDed in DirectoryScanner. To
// revert their logic we wrap them into a <none> selector