This is the frontend to the work-in-progress codepath for upgrading the
source code for a module written for Terraform v0.11 or earlier to use
the new syntax and idiom of v0.12.

The underlying upgrade code is not yet complete as of this commit, and
so the command is not yet very useful. We will continue to iterate on
the upgrade code in subsequent commits.

The remote API this talks to will be going away very soon, before our next
major release, and so we'll remove the command altogether in that release.

This also removes the "encodeHCL" function, which was used only for
adding a .tfvars-formatted file to the uploaded archive.

This allows the user to customize the location where Terraform stores
the files normally placed in the ".terraform" subdirectory, if e.g. the
current working directory is not writable.

For situations where the default network-based discovery is inappropriate
or inconvenient, this allows users to provide a hard-coded discovery
document for a particular hostname in the CLI config.

This is a new config block, rather than combined with the existing
"credentials" block, because credentials should ideally live in separate
files from other config so that they can be managed more carefully.
However, this new "host" block _is_ designed to have room for additional
host-specific configuration _other than_ credentials in future, which
might include TLS certificate overrides or other such things used during
the discovery step.

Now that we are looking into the CLI config file for service host
credentials, it's important to support multiple separate files so that
users can keep credentials separate from other settings and credentials
for different hosts separate from one another.

There is no restriction on which settings can appear in which locations.
This is up to the user to decide, depending on their security needs and
e.g. on whether certain files are generated vs. manually-edited.

The command package is the main place we need access to these, so that
we can use them during init (to install packages, for example) and so that
we can use them to configure remote backends.

For the moment we're just providing an empty credentials object, which
will start to include both statically-configured and
helper-program-provided credentials sources in subsequent commits.

Either the environment variable TF_PLUGIN_CACHE_DIR or a setting in the
CLI config file (~/.terraformrc on Unix) allow opting in to the plugin
caching behavior.

This is opt-in because for new users we don't want to pollute their system
with extra directories they don't know about. By opting in to caching, the
user is assuming the responsibility to occasionally prune the cache over
time as older plugins become stale and unused.

This, in principle, allows us to make use of configuration information
when we populate the Meta structure, though we won't actually make use
of that until a subsequent commit.

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 s...

This command serves as an alternative to the human-oriented list of workspaces for scripting use-cases where it's useful to know the _current_ workspace name.

Feedback after 0.9 was that the term "environment" was confusing due to
it colliding with several other concepts, such as OS environment
variables, a non-aligned Terraform Enterprise concept, and differing ideas
of "environment" within various organizations.

This new term "workspace" is intended to ease some of that confusion. This
term is not used anywhere else in Terraform today, and we expect it to not
be used in a manner that would be confusing within user organizations.

This begins a deprecation cycle for the "terraform env" family of commands,
instead moving to an equivalent set of "terraform workspace" commands.

There are some remaining references to the old "environment" concept in
the code, which will be cleaned up in a separate change. This change is
instead focused on text visible in the UI and wording within code comments
for the benefit of human maintainers of the code.

This new command prints out the tree of modules annotated with their
associated required providers.

The purpose of this command is to help users answer questions such as
"why is this provider required?", "why is Terraform using an older version
of this provider?", and "what combination of modules is creating an
impossible provider version situation?"

For configurations using many modules this sort of question is likely to
come up a lot once we support versioned providers.

As a bonus use-case, this command also shows explicitly when a provider
configuration is being inherited from a parent module, to help users to
understand where the configuration is coming from for each module when
some child modules provide their own provider configurations.

Previously we did plugin discovery in the main package, but as we move
towards versioned plugins we need more information available in order to
resolve plugins, so we move this responsibility into the command package
itself.

For the moment this is just preserving the existing behavior as long as
there are only internal and unversioned plugins present. This is the
final state for provisioners in 0.10, since we don't want to support
versioned provisioners yet. For providers this is just a checkpoint along
the way, since further work is required to apply version constraints from
configuration and support additional plugin search directories.

The automatic plugin discovery behavior is not desirable for tests because
we want to mock the plugins there, so we add a new backdoor for the tests
to use to skip the plugin discovery and just provide their own mock
implementations. Most of this diff is thus noisy rework of the tests to
use this new mechanism.

shouldn't be listed as a common command

Removing the call to StateMeta.Env, so that it doesn't need an embedded
Meta field. Embed Meta and StateMeta separately in all State commands.

Add Env and SetEnv methods to command.Meta to retrieve the current
environment name inside any command.

Make sure all calls to Backend.State contain an environment name, and
make the package compile against the update backend package.

Used a single command with flags for now. We may refactor this out to
subcommands.

Remove the lock command for now to avoid confusion about the behavior of
locks. Rename lock to force-unlock to make it more aparent what it does.

Add a success message, and chose red because it can be a dangerous
operation.

Add confirmation akin to `destroy`, and a `-force` option for
automation and testing.

We have a copy of the output from running just "terraform" in a page on
the website. It doesn't necessarily need to be kept 100% up to date, since
users can always run the command to get the result from the horses mouth,
but it's nice to keep it somewhat up-to-date to reduce use confusion.

Add `terraform debug json2dot` to convert debug log graphs to dot
format. This is not meant to be in place of more advanced debug
visualization, but may continue to be a useful way to work with the
debug output.

This commit adds the `state rm` command for removing an address from
state. It is the result of a rebase from pull-request #5953 which was
lost at some point during the Terraform 0.7 feature branch merges.

Fixes #7259.

Implemented internal plugin calls; which allows us to compile plugins into the main terraform binary

This introduces the terraform state list command to list the resources
within a state. This is the first of many state management commands to
come into 0.7.

This is the first command of many to come that is considered a
"plumbing" command within Terraform (see "plumbing vs porcelain":
http://git.661346.n2.nabble.com/what-are-plumbing-and-porcelain-td2190639.html).
As such, this PR also introduces a bunch of groundwork to support
plumbing commands.

The main changes:

- Main command output is changed to split "common" and "uncommon"
  commands.

- mitchellh/cli is updated to support nested subcommands, since
  terraform state list is a nested subcommand.

- terraform.StateFilter is introduced as a way in core to filter/search
  the state files. This is very basic currently but I expect to make it
  more advanced as time goes on.

- terraform state list command is introduced to list resources in a
  state. This can take a series of arguments to filter this down.

Known issues, or things that aren't done in this PR on purpose:

- Unit tests for terraform state list are on the way. Unit tests for the
  core changes are all there.

 - [x] Docs
 - [x] Command Unit Tests
 - [x] State Unit Tests

Closes #4820

This uses the `fmtcmd` package which has recently been merged into HCL. Per
the usage text, this rewrites Terraform config files to their canonical
formatting and style.

Some notes about the implementation for this initial commit:

- all of the fmtcmd options are exposed as CLI flags
- it operates on all files that have a `.tf` suffix
- it currently only operates on the working directory and doesn't accept a
  directory argument, but I'll extend this in subsequent commits
- output is proxied through `cli.UiWriter` so that we write in the same way
  as other commands and we can capture the output during tests
- the test uses a very simple fixture just to ensure that it is working
  correctly end-to-end; the fmtcmd package has more exhaustive tests
- we have to write the fixture to a file in a temporary directory because it
  will be modified and for this reason it was easier to define the fixture
  contents as a raw string