Image the following task graph which start at 1 and ends at 5:

      1
     /|\
    / | \
   2  3  4
    \ | /
     \|/
      5

Normally, we would do a topographic sort that gives us the order 1 -> 2 -> 3 -> 4 -> 5, but since this example graph is diamond shaped, we could actually run task 2,3 and 4 in parallel, by treating them as a single task which would result in the execution order 1 -> (2 | 3 | 4) -> 5.

Since most tasks in a Cake script probably will be I/O bound, this isn't always what you would want, but theoretically this might shave some seconds of a big build script if applied to the right kind of tasks. We could make this functionality opt-in to prevent it from actually being slower.