Objective

Two repositories exist: repo-a (application source) and repo-b (Kubernetes configuration with values.yaml). When code is pushed to repo-a, the pipeline must build a Docker image tagged with the short Git SHA and update repo-b to use the new tag.

Task

Complete the workflow at /home/interview/repo-a/.github/workflows/promote.yml that triggers on push to main. The repo-b update step is already provided. Add two missing steps: compute the short SHA from $GITHUB_SHA using cut -c1-7 and store it in $GITHUB_ENV as SHORT_SHA, then build a Docker image tagged with $SHORT_SHA.

File Path

• Workflow: /home/interview/repo-a/.github/workflows/promote.yml
• Config: /home/interview/repo-b/values.yaml

name: GitOps Promote

on:
  push:
    branches: [main]

jobs:
  build-and-promote:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Calculate Short SHA
        run: echo "SHORT_SHA=$(echo $GITHUB_SHA | cut -c1-7)" >> $GITHUB_ENV

      - name: Build Docker Image
        run: docker build -t app:$SHORT_SHA .

      - name: Update Repo B
        run: |
          cd /home/interview/repo-b
          sed -i "s/tag: .*/tag: $SHORT_SHA/" values.yaml
          cat values.yaml
          git config user.name "CI Bot"
          git config user.email "[email protected]"
          git add values.yaml
          git commit -m "Promote app:$SHORT_SHA"

Explanation

Step 1: Compute SHA with $GITHUB_ENV

- name: Calculate Short SHA
  run: echo "SHORT_SHA=$(echo $GITHUB_SHA | cut -c1-7)" >> $GITHUB_ENV

$GITHUB_SHA is a built-in GitHub Actions variable containing the full 40-character commit hash. echo $GITHUB_SHA | cut -c1-7 pipes it to cut, which extracts characters 1 through 7 (the short SHA). Writing it to $GITHUB_ENV makes $SHORT_SHA available as an environment variable in all subsequent steps (unlike $GITHUB_OUTPUT which requires steps.<id>.outputs syntax, $GITHUB_ENV creates a regular environment variable).

Step 2: Build and Promote

- name: Build Docker Image
  run: docker build -t app:$SHORT_SHA .

- name: Update Repo B
  run: |
    cd /home/interview/repo-b
    sed -i "s/tag: .*/tag: $SHORT_SHA/" values.yaml
    git config user.name "CI Bot"
    git config user.email "[email protected]"
    git add values.yaml
    git commit -m "Promote app:$SHORT_SHA"

The image is built with the SHA tag. Then we navigate to repo-b and use sed -i to update values.yaml with the new tag. -i edits in place. s/tag: .*/tag: $SHORT_SHA/ substitutes the old tag value with the new SHA. The change is committed as "CI Bot".