Adding ability to pass arguments via args (#107)

This should enable using GitHub Actions `args` attribute to pass
arguments to each action.

Author: sudomateo

README.md

@@ -61,7 +61,7 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 ```
 
-This was a simplified example showing the basic features of these Terraform GitHub Actions. Please refer to the examples within the `examples` directory for more complex usage examples.
+This was a simplified example showing the basic features of these Terraform GitHub Actions. Please refer to the examples within the `examples` directory for more examples of common workflows.
 
 ## Inputs
 
@@ -98,4 +98,4 @@ The usual [Terraform environment variables](https://www.terraform.io/docs/comman
 * [`TF_CLI_ARGS_name`](https://www.terraform.io/docs/commands/environment-variables.html#tf_cli_args-and-tf_cli_args_name)
 * `TF_WORKSPACE`
 
-Other environment variables may be configured to pass data into Terraform backends and providers. If the data is sensitive, consider using [secrets](#secrets) instead.
+Other environment variables may be configured to pass data into Terraform. If the data is sensitive, consider using [secrets](#secrets) instead.

examples/README.md

@@ -0,0 +1,3 @@
+# Examples
+
+Here are some examples showing common workflows using Terraform GitHub Actions.

examples/arguments.md

@@ -0,0 +1,58 @@
+# Arguments 
+
+Arguments can be passed to each subcommand in two ways.
+
+## Using Arguments
+
+GitHub Actions supports an `args` attribute that will pass arguments to the Terraform subcommand. Using this `args` attribute will place the arguments at the end of the entire `terraform` command, even after all of the arguments defined in the source code. In this example, the argument `-var="env=dev"` will be appended to the `terraform init` command.
+
+```yaml
+name: 'Terraform GitHub Actions'
+on:
+  - pull_request
+jobs:
+  terraform:
+    name: 'Terraform'
+    runs-on: ubuntu-latest
+    steps:
+      - name: 'Checkout'
+        uses: actions/checkout@master
+      - name: 'Terraform Init'
+        uses: hashicorp/terraform-github-actions@master
+        with:
+          tf_actions_version: 0.12.13
+          tf_actions_subcommand: 'init'
+          tf_actions_working_dir: '.'
+          tf_actions_comment: true
+        args: '-var="env=dev"'
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+```
+
+
+## Using Environment Variables
+
+Terraform supports environment variables named `TF_CLI_ARGS` and `TF_CLI_ARG_name` where `name` is the subcommand that is being executed. Using these environment variables will place the arguments after the subcommand but before any arguments defined in the source code. In this example, the argument `-var="env=dev"` will be appended to the `terraform init` command.
+
+```yaml
+name: 'Terraform GitHub Actions'
+on:
+  - pull_request
+jobs:
+  terraform:
+    name: 'Terraform'
+    runs-on: ubuntu-latest
+    steps:
+      - name: 'Checkout'
+        uses: actions/checkout@master
+      - name: 'Terraform Init'
+        uses: hashicorp/terraform-github-actions@master
+        with:
+          tf_actions_version: 0.12.13
+          tf_actions_subcommand: 'init'
+          tf_actions_working_dir: '.'
+          tf_actions_comment: true
+        env:
+          TF_CLI_ARGS_init: '-var="env=dev"'
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+```

examples/backends.md

@@ -0,0 +1,28 @@
+# Terraform Backends
+
+Terraform GitHub Actions supports initializing a `backend` block using the `-backend-config` option.
+
+The example below shows how to pass the `token` and `organization` arguments to the `remote` backend block. The `token` argument is passed using GitHub Actions secrets while the organization is hardcoded.
+
+```yaml
+name: 'Terraform GitHub Actions'
+on:
+  - pull_request
+jobs:
+  terraform:
+    name: 'Terraform'
+    runs-on: ubuntu-latest
+    steps:
+      - name: 'Checkout'
+        uses: actions/checkout@master
+      - name: 'Terraform Init'
+        uses: hashicorp/terraform-github-actions@master
+        with:
+          tf_actions_version: 0.12.13
+          tf_actions_subcommand: 'init'
+          tf_actions_working_dir: '.'
+          tf_actions_comment: true
+        args: '-backend-config="token=${{ secrets.TF_API_TOKEN }}" -backend-config="organization=CHANGE_ME"'
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+```