How to prevent Github Actions from deploying on PR with CI/CD

5 min read  •  2020-06-12  •   how-to   devops  •   #github   #github-actions   #ci   #cd

My experience using Github Actions for CI/CD as a solo contributorđź”—

I am using Github Actions to build and deploy my website when I push. That is a classic continuous integration / continuous deployment workflow. It’s convenient to commit, push and have my site build and deploy as a result. This workflow is simple but only works because I am the only contributor.

Github Actions for CI/CD with Pull Requestđź”—

It is a good practice to run sanity checks on pull requests prior to merging. How would that be accomplished with Github Actions?

It turns out that you can do this but you need to be very intentional with how your jobs are configured.

In my workflow, I am designating a main branch main that will run full CI/CD. Build, test and deploy. And for any other branch, just build and test.

I’ll share my example Github Actions workflow file, then I’ll provide a template that you can modify and use for your own purposes.

My example Github Actions workflowđź”—

Here’s my site’s current workflow file for Github Actions. I’ll break this down.

on:
  push:
    branches:
      - main 
  pull_request:
jobs:
  build:
    runs-on: ubuntu-latest
    if: github.ref != 'refs/heads/main'
    steps:
      - name: 'Checkout'
        uses: actions/checkout@main
      - name: 'Build only'
        uses: tjtelan/zola-deploy-action@main
        env:
          BUILD_DIR: .
          TOKEN: ${{ secrets.TOKEN }}
          BUILD_ONLY: true
  build_and_deploy:
    runs-on: ubuntu-latest
    if: github.ref == 'refs/heads/main'
    steps:
      - name: 'Checkout'
        uses: actions/checkout@main
      - name: 'Build and deploy'
        uses: tjtelan/zola-deploy-action@main
        env:
          PAGES_BRANCH: gh-pages 
          BUILD_DIR: .
          TOKEN: ${{ secrets.TOKEN }}

At the top, I am specifying the events that I want to trigger on with the on top-level key.

on:
  push:
    branches:
      - main 
  pull_request:

I want to trigger on push events to the main branch, and all pull requests.

Later below are 2 jobs that are almost identical. I’ll break them down one at a time then compare their differences.

build job 

  build:
    runs-on: ubuntu-latest
    if: github.ref != 'refs/heads/main'
    steps:
      - name: 'Checkout'
        uses: actions/checkout@main
      - name: 'Build only'
        uses: tjtelan/zola-deploy-action@main
        env:
          BUILD_DIR: .
          TOKEN: ${{ secrets.TOKEN }}
          BUILD_ONLY: true
  1. This job uses the ubuntu-latest github hosted runner as my environment.
  2. I do a check for the git ref via the github.ref key. Or another way to say this is I check that the working branch that triggered this job is not the main branch. I’ll continue forward only if this condition is true.
  3. Lastly are my steps. I use the actions/checkout@main marketplace action to check my code out, and I use my fork of an action for Zola called tjtelan/zola-deploy-action@main. I have an environment variable BUILD_ONLY set to true which results in building my site but not deploying it.

build_and_deploy job

  build_and_deploy:
    runs-on: ubuntu-latest
    if: github.ref == 'refs/heads/main'
    steps:
      - name: 'Checkout'
        uses: actions/checkout@main
      - name: 'Build and deploy'
        uses: tjtelan/zola-deploy-action@main
        env:
          PAGES_BRANCH: gh-pages 
          BUILD_DIR: .
          TOKEN: ${{ secrets.TOKEN }}
  1. This job also uses the ubuntu-latest github hosted runner as my environment.
  2. I do a similar check for the git ref via the github.ref key. This time I am looking for the working branch to be main
  3. Lastly are my steps. Same as the previous job, but I am configuring tjtelan/zola-deploy-action@main differently. Rather than setting BUILD_ONLY, I am defining PAGES_BRANCH to gh-pages, which is where I want to deploy my site code after build.

Last words on job differencesđź”—

The only differences are the branch check via github.ref, and the specifics of steps. I happen to be using my own Github Action tjtelan/zola-deploy-action but your steps could consist of anything you want to do differently between pull requests and push to your “special” branch.

Github Actions templateđź”—

on:
  push:
    branches:
      - main
  pull_request:
jobs:
  build:
    runs-on: ubuntu-latest
    if: github.ref != 'refs/heads/main
    steps:
      - name: 'Checkout'
        uses: actions/checkout@main
  build_and_deploy:
    runs-on: ubuntu-latest
    if: github.ref == 'refs/heads/main
    steps:
      - name: 'Checkout'
        uses: actions/checkout@main

Here’s a template that you can use for your own push vs PR workflows. By default, I assume main as the special branch, so you’ll need to change that if you want to use a different branch. Additionally, you’ll need to provide all the steps to take after checking code out.

Sourcesđź”—