📚 Add examples of using the issue_comment event

Author: dflook

terraform-apply/README.md

@@ -226,3 +226,34 @@ jobs:
           auto_approve: true
           target: kubernetes_secret.tls_cert_public,kubernetes_secret.tls_cert_private
 ```
+
+### Applying a plan using a comment
+
+This workflow applies a plan on demand, triggered by someone
+commenting `terraform apply` on the PR. The plan is taken
+from an existing comment generated by the [`dflook/terraform-plan`](https://github.com/dflook/terraform-github-actions/tree/master/terraform-plan)
+action.
+
+```yaml
+name: Terraform Apply
+
+on: [issue_comment]
+
+jobs:
+  plan:
+    if: github.event.issue.pull_request && contains(github.event.comment.body, 'terraform apply')
+    runs-on: ubuntu-latest
+    name: Apply terraform plan
+    env:
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          ref: refs/pull/${{ github.event.issue.number }}/merge
+
+      - name: terraform apply
+        uses: dflook/terraform-apply@v1
+        with:
+          path: my-terraform-config
+```

terraform-plan/README.md

@@ -111,6 +111,8 @@ The [dflook/terraform-apply](https://github.com/dflook/terraform-github-actions/
 
 ## Example usage
 
+### Automatically generating a plan
+
 This example workflow runs on every push to an open pull request,
 and create or updates a comment with the terraform plan
 
@@ -134,3 +136,33 @@ jobs:
         with:
           path: my-terraform-config
 ```
+
+### Generating a plan using a comment
+
+This workflow generates a plan on demand, triggered by someone
+commenting `terraform plan` on the PR. The action will create or update
+a comment on the PR with the generated plan.
+
+```yaml
+name: Terraform Plan
+
+on: [issue_comment]
+
+jobs:
+  plan:
+    if: github.event.issue.pull_request && contains(github.event.comment.body, 'terraform plan')
+    runs-on: ubuntu-latest
+    name: Create terraform plan
+    env:
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          ref: refs/pull/${{ github.event.issue.number }}/merge
+
+      - name: terraform plan
+        uses: dflook/terraform-plan@v1
+        with:
+          path: my-terraform-config
+```