// shift the partial diffs to the absolute document positions
for (Iterator it= diffs.iterator(); it.hasNext();) {
RangeDifference d= (RangeDifference) it.next();
d.shiftLeft(leftStartLine);
d.shiftRight(rightStartLine);
}
// undo optimization shifting
if (shiftBefore > 0) {
RangeDifference first= (RangeDifference) diffs.get(0);