For a long time now we've been advising against the use of provisioners,
but our documentation for them is pretty prominent on the website in
comparision to the better alternatives, and so it's little surprise that
many users end up making significant use of them.
Although in the longer term a change to our information architecture would
probably address this even better, this is an attempt to be explicit about
the downsides of using provisioners and to prominently describe the
alternatives that are available for common use-cases, along with some
reasons why we consider them to be better.
I took the unusual step here of directly linking to specific provider
documentation pages about the alternatives, even though we normally try
to keep the core documentation provider-agnostic, because otherwise that
information tends to be rather buried in the provider documentation and
thus the reader would be reasonable to use provisioners just because we're
not giving specific enough alternative recommendations.
This new argument allows overriding of the working directory of the child process, with the default still being the working directory of Terraform itself.
Martin Atkins