feat: add file-exists action

.github/workflows/_test-file-exists-action.yml

@@ -0,0 +1,59 @@
+name: Test File Exists Action
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - "actions/file-exists/**"
+  pull_request:
+    paths:
+      - "actions/file-exists/**"
+
+permissions:
+  contents: read
+
+jobs:
+  test-file-exists:
+    runs-on: ${{ matrix.os }}
+    name: Test File Exists Action (${{ matrix.os }})
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Test with existing file
+        uses: ./actions/file-exists
+        with:
+          file: README.md
+
+  test-failure-case:
+    runs-on: ${{ matrix.os }}
+    name: Test File Not Exists (${{ matrix.os }})
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Test with non-existent file
+        uses: ./actions/file-exists
+        with:
+          file: this-file-does-not-exist.txt
+        continue-on-error: true
+        id: nonexistent
+
+      - name: Verify action failed as expected
+        if: steps.nonexistent.outcome == 'failure'
+        run: echo "✅ Action correctly failed when file doesn't exist"
+
+      - name: Fail job if action didn't fail
+        if: steps.nonexistent.outcome != 'failure'
+        run: |
+          echo "❌ Action should have failed but didn't"
+          exit 1

README.md

@@ -22,6 +22,8 @@ This repository serves as a comprehensive toolkit for creating and managing GitH
 
 - **[.github/workflows](/.github/workflows)**: GitHub Actions workflows for automating common parts of Skills Exercises
 - **[markdown-templates](/markdown-templates)**: Ready-to-use Markdown templates for creating consistent exercise documentation, instructions, and README files
+- **[actions](/actions)**: Simple composite actions to help when building GitHub Skills exercises
+
 
 ## Examples
 

actions/file-exists/README.md

@@ -0,0 +1,22 @@
+# File Exists :package:
+
+A GitHub Action that checks if a file exists in the repository.
+
+This action will fail if the file does not exist
+
+## Inputs ⚙️
+
+| Name   | Description                                                    | Required |
+| ------ | -------------------------------------------------------------- | -------- |
+| `file` | The path to the file to check, relative to the repository root | Yes      |
+
+## Usage 🚀
+
+```yaml
+steps:
+  - uses: actions/checkout@v4
+  - name: Check if file exists
+    uses: skills/exercise-toolkit/actions/file-exists@<git-tag>
+    with:
+      file: "path/to/your/file.md"
+```

actions/file-exists/action.yml

@@ -0,0 +1,25 @@
+name: "File Exists"
+description: "Checks if a file exists in the repository"
+inputs:
+  file:
+    description: "The path to the file to check"
+    required: true
+runs:
+  using: "composite"
+  steps:
+    - name: Check if file exists
+      uses: actions/github-script@v7
+      env:
+        FILE_PATH: ${{ inputs.file }}
+      with:
+        script: |
+          const fs = require('fs');
+          const path = require('path');
+          const filePath = path.join(process.env.GITHUB_WORKSPACE, process.env.FILE_PATH);
+
+          if (!fs.existsSync(filePath)) {
+            core.setFailed(`❌ File does not exist: ${filePath}`);
+            return;
+          }
+
+          console.log(`✅ File exists: ${filePath}`);