Extract target specs from a manifest for BuildAndDeploy.

Go through all the manifests, and check: 1) all pending file changes 2) all pending dependency changes (where an image has been rebuilt by another manifest), and 3) all pending manifest changes The earliest one is the one we want.

Grab all the targets that are build-eligible from the engine state.

Hold back live update targets that are being successfully handled by a reconciler.

We use the cluster to detect what architecture we're building for.

In automatic trigger mode: - Clicking the trigger button always triggers a full rebuild.

Algorithm to choose a manifest to build next.

Helper function for ordering targets that have never been built before.

Something is wrong enough that we shouldn't bother falling back to other BaD's -- they won't work.

TODO(maia): CommandRunner interface for testability.

Nothing is on fire, this is an expected case like a container builder being passed a build with no attached container.

A little data structure to help iterate through dirty targets in dependency order.

Allows the caller to inject its own build strategy for dirty targets.