Updating README with example (#89)

Author: sudomateo

README.md

@@ -2,24 +2,75 @@
 
 Terraform GitHub Actions allow you to run Terraform commands within GitHub Actions.
 
-The output of the actions can be viewed from the Actions tab in the main repository view. If the actions are executed on a `pull_request` event, a comment may be posted on the pull request.
+The output of the actions can be viewed from the Actions tab in the main repository view. If the actions are executed on a pull request event, a comment may be posted on the pull request.
 
 ## Success Criteria
 
 An exit code of `0` is considered a successful execution.
 
 ## Usage
 
-Please refer to the examples within the `examples` directory for usage.
+The most common use case is to run `terraform fmt`, `terraform init`, `terraform validate`, and `terraform plan` on a pull request. A comment will be posted to the pull request depending on the output of the Terraform command being executed.
+
+```yaml
+name: 'Terraform Pull Request Workflow'
+on:
+  - pull_request
+jobs:
+  example:
+    name: 'Terraform Actions'
+    runs-on: ubuntu-latest
+    steps:
+      - name: 'Checkout'
+        uses: actions/checkout@master
+      - name: 'Terraform Format'
+        uses: hashicorp/terraform-github-actions@master
+        with:
+          tf_actions_version: 0.12.13
+          tf_actions_subcommand: 'fmt'
+          tf_actions_working_dir: '.'
+          tf_actions_comment: true
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      - 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:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      - name: 'Terraform Validate'
+        uses: hashicorp/terraform-github-actions@master
+        with:
+          tf_actions_version: 0.12.13
+          tf_actions_subcommand: 'validate'
+          tf_actions_working_dir: '.'
+          tf_actions_comment: true
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      - name: 'Terraform Plan'
+        uses: hashicorp/terraform-github-actions@master
+        with:
+          tf_actions_version: 0.12.13
+          tf_actions_subcommand: 'plan'
+          tf_actions_working_dir: '.'
+          tf_actions_comment: true
+        env:
+          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.
 
 ## Inputs
 
-| Name                     | Required | Default | Description                                 |
-|--------------------------|----------|---------|---------------------------------------------|
-| `tf_actions_version`     | `true`   |         | Terraform version to install.               |
-| `tf_actions_subcommand`  | `true`   |         | Terraform subcommand to execute.            |
-| `tf_actions_working_dir` | `false`  | `.`     | Terraform working directory.                |
-| `tf_actions_comment`     | `false`  | `true`  | Whether or not to comment on pull requests. |
+| Name                     | Required | Default | Description                                                                                       |
+|--------------------------|----------|---------|---------------------------------------------------------------------------------------------------|
+| `tf_actions_version`     | `true`   |         | Terraform version to install and execute.                                                         |
+| `tf_actions_subcommand`  | `true`   |         | Terraform subcommand to execute. Valid values are `fmt`, `init`, `validate`, `plan`, and `apply`. |
+| `tf_actions_working_dir` | `false`  | `.`     | The working directory to change into before executing Terraform commands.                         |
+| `tf_actions_comment`     | `false`  | `true`  | Whether or not to comment on pull requests.                                                       |
 
 ## Outputs
 
@@ -39,7 +90,7 @@ Other secrets may be needed to authenticate with Terraform backends and provider
 
 ## Environment Variables
 
-The usual [Terraform environment variables](https://www.terraform.io/docs/commands/environment-variables.html) are supported. Here are the environments variables that might be the most beneficial.
+The usual [Terraform environment variables](https://www.terraform.io/docs/commands/environment-variables.html) are supported. Here are the environment variables that might be the most beneficial.
 
 * [`TF_LOG`](https://www.terraform.io/docs/commands/environment-variables.html#tf_log)
 * [`TF_VAR_name`](https://www.terraform.io/docs/commands/environment-variables.html#tf_var_name)