The documentation for the -target option warns that it's intended for
exceptional circumstances only and not for routine use, but that's not a
very prominent location for that warning and so some users miss it.

Here we make the warning more prominent by including it directly in the
Terraform output when -target is in use. We first warn during planning
that the plan might be incomplete, and then warn again after apply
concludes and direct the user to run "terraform plan" to make sure that
there are no further changes outstanding. The latter message is intended
to reinforce that -target should only be a one-off operation and that you
should always run without it soon after to ensure that the workspace is
left in a consistent, converged state.