Order stacks by their references

A StackReference makes one stack read another’s outputs:

const net = new pulumi.StackReference("acme/network/prod");
const vpcId = net.getOutput("vpcId");

plywood reads each stack’s references from its last export and orders the waves by them, so network/prod updates before the stacks that read it. A stack’s first update has no export yet, and outputs that are all secret show no reference, so give that order by hand:

waves:
  canary: [app/dev]
  after:
    app/prod: [network/prod]

canary puts its stacks in a first wave of their own. plywood init prints each order it found, and each reference to a stack this repository does not list.