long baseRevision = revNum - 1;
if (!SVNRevision.isValidRevisionNumber(baseRevision)) {
SVNErrorMessage err = SVNErrorMessage.create(SVNErrorCode.FS_NO_SUCH_REVISION, "Invalid base revision {0}", new Long(baseRevision));
SVNErrorManager.error(err, SVNLogType.FSFS);
}
SVNNodeEditor editor = generateDeltaTree(fsfs, root, baseRevision);
ISVNGNUDiffGenerator generator = getDiffGenerator();
generator.setDiffAdded(diffAdded);
generator.setDiffCopied(diffCopyFrom);
generator.setDiffDeleted(diffDeleted);
editor.diff(root, baseRevision, generator, os);
}