feat(07-expressions): add README

.github/workflows/07-expressions.yaml

@@ -1,3 +1,6 @@
+# See 07-expressions/README.md for more information
+# about the how to use expressions in GitHub Actions.
+
 name: 07 - Using Expressions
 run-name: 07 - Using Expressions | DEBUG - ${{ inputs.debug && 'ON' || 'OFF' }}
 

07-expressions/README.md

@@ -0,0 +1,57 @@
+# Using Expressions in GitHub Actions
+
+GitHub Actions provides a powerful feature called expressions that allows you to dynamically evaluate and manipulate data within your workflows. Expressions enable you to create more flexible and intelligent automation. This README provides an overview of how to use expressions effectively in GitHub Actions.
+
+## Understanding Expressions
+
+Expressions in GitHub Actions are enclosed within `${{ }}` and can be used to access and transform data from GitHub contexts, environment variables, inputs, and more. They are evaluated at runtime and can be used in various workflow scenarios, such as conditional statements, setting variables, or generating dynamic content.
+
+## Common Use Cases
+
+Here are some common use cases for using expressions in GitHub Actions:
+
+### 1. Dynamic Variable Assignment
+
+You can use expressions to assign dynamic values to variables within your workflow:
+
+```yaml
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set Variable Using an Expression
+        run: |
+          # Define a dynamic variable using an expression
+          MY_VAR="Hello, ${{ github.actor }}!"
+
+          # Use the variable in an echo statement
+          echo $MY_VAR
+```
+
+## 2. Conditional Steps
+
+Expressions allow you to create conditional steps based on GitHub context or other data:
+
+```yaml
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Conditional Step Using an Expression
+        run: |
+          if [[ "${{ github.event_name }}" == "push" && "${{ github.ref }}" == "refs/heads/main" ]]; then
+            echo "This is a push to the main branch."
+          fi
+```
+
+We can also use expressions in `if` statements when deciding whether to execute a step or a job. Under the `if` key, we don't need to add the special `${{ <expression> }}` syntax.
+
+```yaml
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Conditional Step Using an Expression
+        if: github.event_name == "push" && github.ref == "refs/heads/main"
+        run: echo "This is a push to the main branch."
+```