Update Readme

Author: owjs3901

README.md

@@ -1 +1,41 @@
-# github-action-template
+# Overwrite Env File
+
+This GitHub Action allows you to overwrite the contents of an environment file with the contents of another file. It is useful when you want to promote/stage environment variables from one environment to another (for example, from a `.env.development` file to a `.env.production` file) automatically in your workflows.
+
+## Usage
+
+```yaml
+- name: Overwrite production env file with development env file
+  uses: ./action-tools/overwrite-env-file
+  with:
+    input: .env.development
+    output: .env.production
+```
+
+#### Inputs
+
+| Name         | Description                  | Required | Default             |
+|--------------|------------------------------|----------|---------------------|
+| input   | The file to read from        | true     | .env.development    |
+| output  | The file to overwrite to     | true     | .env.production     |
+
+## Example Workflow
+
+```yaml
+name: Promote env to production
+
+on:
+  push:
+    branches: [main, dev]
+
+jobs:
+  promote-env:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Overwrite production env file with development env file
+        uses: dev-five-git/overwrite-env-file-action@v1
+        if: github.ref_name == 'dev'
+```