The bulk of the text on this page hasn't been revised for some time and
so parts of it were using non-idiomatic terminology or not defining terms
at all.
The main goal of this revision is to standardize on the following terms:
- "provider configuration" refers to a specific provider block in config,
as a distinct idea from the provider _itself_, which is a singleton.
- "Default" vs. "additional" provider configurations, distinguishing
those without and with "alias" arguments respectively. These are named
here so that we can use this terminology to describe the different
behaviors of each for the purposes of provider inheritance between
modules.
Since we don't currently auto-install provisioner plugins this is
currently placed on the providers documentation page and referred to as
the "Provider Plugin Cache". In future this mechanism may also apply to
provisioners, in which case we'll figure out at that point where better
to place this information so it can be referenced from both the provider
and provisioner documentation pages.
This mechanism for configuring plugins is now deprecated, since it's not
capable of declaring plugin versions. Instead, we recommend just placing
plugins into a particular directory, which is now documented on the
main providers documentation page and linked from the more detailed docs
on plugins in general.
Previously the -upgrade option was covered only on the "terraform init" usage page. It seems also worth mentioning in the main docs on provider versioning, since we're already explaining here other mechanics of the versioning/constraints system.
Andrei Ivanov