When a user specifies `-target`s on a `terraform plan` and stores
the resulting diff in a plan file using `-out` - it usually works just
fine since the diff is scoped based on the targets.
When there are tainted resources in the state, however, graph nodes to
destroy them were popping back into the plan when it was being loaded
from a file. This was because Targets weren't being stored in the
Planfile, so Terraform didn't know to filter them out. (In the
non-Planfile scenario, we still had the Targets loaded directly from the
flags.)
By encoding Targets in with the Planfile we can ensure that the same
filters are always applied.
Backwards compatibility should be fine here, since we're just adding a
field. The gob encoder/decoder will just do the right thing (ignore/skip
the field) with planfiles stored w/ versions that don't know about
Targets.
Fixes#5183
Add `-target=resource` flag to core operations, allowing users to
target specific resources in their infrastructure. When `-target` is
used, the operation will only apply to that resource and its
dependencies.
The calculated dependencies are different depending on whether we're
running a normal operation or a `terraform destroy`.
Generally, "dependencies" refers to ancestors: resources falling
_before_ the target in the graph, because their changes are required to
accurately act on the target.
For destroys, "dependencies" are descendents: those resources which fall
_after_ the target. These resources depend on our target, which is going
to be destroyed, so they should also be destroyed.
This is REALLY heavy and would be really hard to maintain any sort
of compatibility with, but it is what we're going to do during dev
initially (if we don't ship with it) in order to just get stuff working.
