Use System.arraycopy to copy parent object id array

Change-Id: Iee475584f0a65b8b77610cd277f15295b68dfe80

org.eclipse.jgit/src/org/eclipse/jgit/lib/CommitBuilder.java

@@ -204,8 +204,7 @@ public class CommitBuilder {
 			setParentId(additionalParent);
 		} else {
 			ObjectId[] newParents = new ObjectId[parentIds.length + 1];
-			for (int i = 0; i < parentIds.length; i++)
+			System.arraycopy(parentIds, 0, newParents, 0, parentIds.length);
-				newParents[i] = parentIds[i];
 			newParents[parentIds.length] = additionalParent.copy();
 			parentIds = newParents;
 		}