In #15884 we adjusted the plan output to give an explicit command to run
to apply a plan, whereas before this command was just alluded to in the
prose.
Since releasing that, we've got good feedback that it's confusing to
include such instructions when Terraform is running in a workflow
automation tool, because such tools usually abstract away exactly what
commands are run and require users to take different actions to
proceed through the workflow.
To accommodate such environments while retaining helpful messages for
normal CLI usage, here we introduce a new environment variable
TF_IN_AUTOMATION which, when set to a non-empty value, is a hint to
Terraform that it isn't being run in an interactive command shell and
it should thus tone down the "next steps" messaging.
The documentation for this setting is included as part of the "...in
automation" guide since it's not generally useful in other cases. We also
intentionally disclaim comprehensive support for this since we want to
avoid creating an extreme number of "if running in automation..."
codepaths that would increase the testing matrix and hurt maintainability.
The focus is specifically on the output of the three commands we give in
the automation guide, which at present means the following two situations:
* "terraform init" does not include the final paragraphs that suggest
running "terraform plan" and tell you in what situations you might need
to re-run "terraform init".
* "terraform plan" does not include the final paragraphs that either
warn about not specifying "-out=..." or instruct to run
"terraform apply" with the generated plan file.
We are changing the behaviour of the "stub" diff operation to just have
the pre/post-diff hooks skipped on eval, meaning that the test against
CountHook will ultimately be meaningless and fail, hence we need a
different test here that tests it on a more general level.
Fixes#11504
The local backend should error if `terraform plan` is called in a
directory with no Terraform config files (same behavior as 0.8.x).
**New behavior:** We now allow `terraform plan -destroy` with no
configuration files since that seems reasonable.
The local backend implementation is an implementation of
backend.Enhanced that recreates all the behavior of the CLI but through
the backend interface.
James Bardin