Fix DeltaTask infinite loop

DeltaTask$Block.partitionTask was doing an infinite loop if number of
threads was greater than the totalWeight. The weightPerThread was 0
which was causing the infinite loop. Set the weightPerThread to a
minimal value of one.

Bug: 420915
Change-Id: Ia8e3ad956d53d8193937b7fa1bc19aafde9767ff
Signed-off-by: Hugo Arès <hugo.ares@ericsson.com>

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/DeltaTask.java

@@ -121,7 +121,7 @@ final class DeltaTask implements Callable<Object> {
 			ArrayList<WeightedPath> topPaths = computeTopPaths();
 			Iterator<WeightedPath> topPathItr = topPaths.iterator();
 			int nextTop = 0;
-			long weightPerThread = totalWeight / threads;
+			long weightPerThread = Math.max(totalWeight / threads, 1);
 			for (int i = beginIndex; i < endIndex;) {
 				DeltaTask task = new DeltaTask(this);
 				long w = 0;