This PR adds a new `pulumi history` command, which prints the update history for a stack.
The local backend stores the update history in a JSON file on disk, next to the checkpoint file. The cloud backend simply provides the update metadata, and expects to receive all the data from a (NYI) `/history` REST endpoint.
`pkg/backend/updates.go` defines the data that is being persisted. The way the data is wired through the system is adding a new `backend.UpdateMetadata` parameter to a Stack/Backend's `Update` and `Destroy` methods.
I use `tests/integration/stack_outputs/` as the simple app for the related tests, hence the addition to the `.gitignore` and fixing the name in the `Pulumi.yaml`.
Fixes#636.
The two-phase output properties change broke the ability to recover
from a failed replacement that yields pending deletes in the checkpoint.
The issue here is simply that we should remember pending registrations
only for logical operations that *also* have a "new" state (create or
update). This commit fixes this, and also adds a new step test with
fault injection to probe many interesting combinations of steps.