added new composite action exercise

labs/composite-action.md

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+# Composite Actions
+In this hands-on lab, you will create a composite action and a workflow that consumes it.
+
+You will learn how to define an action, pass inputs to it, and use its outputs in the calling workflow. This is a great way to bundle multiple steps into a single, reusable command.
+
+This hands-on lab consists of the following steps:
+
+- Creating the action file
+
+- Adding inputs and outputs
+
+- Consuming the composite action
+
+## Creating the action file
+First, create a directory for your action. By convention, local actions are stored in the `.github/actions` directory. Create a new directory named `greet-action` inside `.github/actions`.
+
+Create a new file inside that directory: `.github/actions/greet-action/action.yml`.
+
+Set the name and description for your action. You can see an example below. 
+
+```YAML
+name: 'Greet and Set Time Action'
+description: 'A composite action that greets someone and outputs the time.'
+```
+
+Add a `runs` block that specifies using: `composite` and add a single step that echoes "Hello". 
+
+<details>
+<summary>Solution</summary>
+
+```YAML
+runs:
+  using: 'composite'
+  steps:
+    - name: Greet someone
+      run: echo "Hello ${{ inputs.who-to-greet }}"
+      shell: bash
+
+```
+</details>
+
+## Adding inputs and outputs
+Add an inputs block to your `action.yml`. Define an input named `who-to-greet` that is a required string with a default value of World. Then, update the `run` command to use this input.
+
+<details>
+<summary>Solution</summary>
+
+```YAML
+inputs:
+  who-to-greet:
+    description: 'The person to greet'
+    type: string
+    required: true
+    default: 'World'
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Greet someone
+      run: echo "Hello ${{ inputs.who-to-greet }}"
+      shell: bash
+```
+</details>
+
+Add a second step with the `id` of `time`. This step will use a workflow command to set an output parameter named `current-time` to the current date.
+
+<details>
+<summary>Solution</summary>
+
+```YAML
+    - name: Set time
+      id: time
+      run: echo "time=$(date)" >> $GITHUB_OUTPUT
+      shell: bash
+```
+</details>
+
+Finally, add an `outputs` block to the `action.yml`. Define an output called `current-time` and set its value to the output from the `time` step.
+
+<details>
+<summary>Solution</summary>
+
+outputs:
+```YAML
+  current-time:
+    description: 'The time when greeting.'
+    value: ${{ steps.time.outputs.time }}
+```
+</details>
+
+
+<summary>Complete action.yml Solution</summary>
+
+```YAML
+name: 'Greet and Set Time Action'
+description: 'A composite action that greets someone and outputs the time.'
+
+inputs:
+  who-to-greet:
+    description: 'The person to greet'
+    type: string
+    required: true
+    default: 'World'
+
+outputs:
+  current-time:
+    description: 'The time when greeting.'
+    value: ${{ steps.time.outputs.time }}
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Greet someone
+      run: echo "Hello ${{ inputs.who-to-greet }}"
+      shell: bash
+
+    - name: Set time
+      id: time
+      run: echo "time=$(date)" >> $GITHUB_OUTPUT
+      shell: bash
+```
+</details>
+
+## Consuming the composite action
+Create a new file named `.github/workflows/test-composite.yml`.
+
+Set the name to `Test Composite Action` and add a manual `workflow_dispatch` trigger.
+
+<details>
+<summary>Solution</summary>
+
+```YAML
+name: Test Composite Action
+
+on: [workflow_dispatch]
+```
+</details>
+
+Add a job named `run-action`. The first step must be `actions/checkout@v4` so your workflow can find your local composite action in the repository.
+
+<details>
+<summary>Solution</summary>
+
+```YAML
+jobs:
+  run-action:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+```
+</details>
+
+Add a second step to call your composite action. Give the step an `id` (e.g., greet_step) so you can access its outputs. Use the `with` keyword to pass in your username as the `who-to-greet` input. We can use the  `${{ github.actor }}` context to automatically add the username of the person who triggered the workflow.
+
+
+<details>
+<summary>Solution</summary>
+
+```YAML
+      - name: Run my composite action
+        id: greet_step
+        uses: ./.github/actions/greet-action
+        with:
+          who-to-greet: '${{ github.actor }}'
+```
+</details>
+
+Add a final step to echo the `current-time` output from your action step.
+
+```YAML
+    - name: Use the output
+      run: echo "The time was ${{ steps.greet_step.outputs.current-time }}"
+```
+
+
+
+<details>
+<summary>Complete solution</summary>
+
+```YAML
+
+name: Test Composite Action
+
+on: [workflow_dispatch]
+
+jobs:
+  run-action:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Run my composite action
+        id: greet_step
+        uses: ./.github/actions/greet-action
+        with:
+          who-to-greet: '${{ github.actor }}'
+
+      - name: Use the output
+        run: echo "The time was ${{ steps.greet_step.outputs.current-time }}"
+
+```
+</details>
+
+
+Commit your files, run the workflow, and observe the output.
+
+# Summary
+
+In this lab, you have learned how to create a composite action that bundles multiple steps. 
+You also learned how to define inputs and outputs for the action and how to call it from a workflow. 
+Unlike reusable workflows which replace an entire job, composite actions act as a single, powerful step inside any job you choose.
+
+If you are interested in trying out writing a Docker action, check out this exercise as part of the [GitHub official Github Actions training](https://github.com/ps-actions-sandbox/ActionsFundamentals)