refactor: use infracost CI scripts (#12)

README.md

@@ -1,6 +1,8 @@
 # Infracost GitHub Action
 
-This GitHub Action runs [Infracost](https://infracost.io) against the master branch and the pull request whenever a Terraform file changes. It automatically adds a pull request comment showing the cost estimate difference (similar to `git diff`) if a percentage threshold is crossed.
+This GitHub Action runs [Infracost](https://infracost.io) against the master/main branch and the pull request whenever a Terraform file changes. It automatically adds a pull request comment showing the cost estimate difference (similar to `git diff`) if a percentage threshold is crossed.
+
+This Action uses the latest version of Infracost by default as we continually add support for more cloud resources.
 
 <img src="screenshot.png" width=557 alt="Example screenshot" />
 
@@ -52,13 +54,13 @@ If the [Terraform directory method](https://www.infracost.io/docs/#1-terraform-d
 
 ## Outputs
 
-### `master_monthly_cost`
+### `default_branch_monthly_cost`
 
-The master branch's monthly cost estimate.
+The default branch's monthly cost estimate.
 
-### `pull_request_monthly_cost`
+### `current_branch_monthly_cost`
 
-The pull request's monthly cost estimate.
+The current branch's monthly cost estimate.
 
 ## Usage
 
@@ -78,26 +80,20 @@ The pull request's monthly cost estimate.
       runs-on: ubuntu-latest
       name: Show infracost diff
       steps:
-      - name: Checkout master branch
-        uses: actions/checkout@v2
-        with:
-          ref: master
-          path: master
-      - name: Checkout pull request branch
+      - name: Check out repository
         uses: actions/checkout@v2
-        with:
-          ref: ${{ github.event.pull_request.head.sha }}
-          path: pull_request
       - name: Run infracost diff
-        uses: infracost/infracost-gh-action@master # Use a specific version if locking the GH Action version is preferred
+        uses: infracost/infracost-gh-action@master # Use a specific version instead of master if locking is preferred
         env:
           INFRACOST_API_KEY: ${{ secrets.INFRACOST_API_KEY }}
           AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
           AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} # Do not change
         with:
+          entrypoint: /scripts/ci/diff.sh # Do not change
           tfdir: PATH/TO/CODE
           tfflags: -var-file=myvars.tfvars
+          percentage_threshold: 1
   ```
 
 ## Contributing

action.yml

@@ -35,7 +35,7 @@ outputs:
     description: The pull request's monthly cost estimate.
 runs:
   using: docker
-  image: Dockerfile
+  image: docker://infracost/infracost:latest # Use a specific version instead of latest if locking is preferred
   args:
     - ${{ inputs.tfjson }}
     - ${{ inputs.tfplan }}