only relevant to job allocations.

Add -T/--task-layout-byid which allows task layout by relative nodeid with the
  allocation.  For instance, given nodes foo[1-16] in an allocation, the command
  slaunch -T 1,[3-4],1,3,8,-1,0,-1 will run on tasks on nodes in the following
  order: foo[2,4-5,2,4,9,16,1,16]
  Notice that negative numbers are permitted.

Task layout by nodename is now -Y/--task-layout-byname.

The --relative option now allows a negative number.  -1 is the last node in
the allocation.