In the 0.10 release we added an opt-in mode where Terraform would prompt
interactively for confirmation during apply. We made this opt-in to give
those who wrap Terraform in automation some time to update their scripts
to explicitly opt out of this behavior where appropriate.
Here we switch the default so that a "terraform apply" with no arguments
will -- if it computes a non-empty diff -- display the diff and wait for
the user to type "yes" in similar vein to the "terraform destroy" command.
This makes the commonly-used "terraform apply" a safe workflow for
interactive use, so "terraform plan" is now mainly for use in automation
where a separate planning step is used. The apply command remains
non-interactive when given an explicit plan file.
The previous behavior -- though not recommended -- can be obtained by
explicitly setting the -auto-approve option on the apply command line,
and indeed that is how all of the tests are updated here so that they can
continue to run non-interactively.
Martin Atkins