terraform: fix cycle that could happen during destroy

terraform/graph.go

@@ -284,12 +284,9 @@ func graphAddDiff(g *depgraph.Graph, d *Diff) error {
 			newNode.Resource.Diff = &ResourceDiff{Destroy: true}
 
 			// Append it to the list so we handle it later
-			deps := make([]*depgraph.Dependency, len(n.Deps))
-			copy(deps, n.Deps)
 			newN := &depgraph.Noun{
 				Name: fmt.Sprintf("%s (destroy)", newNode.Resource.Id),
 				Meta: newNode,
-				Deps: deps,
 			}
 			nlist = append(nlist, newN)
 

terraform/graph_test.go

@@ -276,6 +276,7 @@ const testTerraformGraphDiffDestroyStr = `
 root: root
 aws_instance.bar
   aws_instance.bar -> aws_instance.bar (destroy)
+  aws_instance.bar -> aws_instance.foo
 aws_instance.bar (destroy)
 aws_instance.foo
   aws_instance.foo -> aws_instance.foo (destroy)

terraform/test-fixtures/graph-diff-destroy/main.tf

@@ -1,2 +1,6 @@
 resource "aws_instance" "foo" {
 }
+
+resource "aws_instance" "bar" {
+    foo = "${aws_instance.foo.id}"
+}