if (fp.first() != NO_REVISION && fp.second() == NO_REVISION && !isNewFile) {
// compare file contents to see if anything has changed, and reuse old revision, if unchanged.
// XXX ineffective, need better access to revision conten
ByteArraySerializer bas = new ByteArraySerializer();
bds.serialize(bas);
final byte[] newContent = bas.toByteArray();
// unless there's a way to reset DataSource, replace it with the content just read
bds = new DataSerializer.ByteArrayDataSource(newContent);
if (new ComparatorChannel(newContent).same(df, fp.first())) {
fileRev = df.getRevision(fp.first());
}