ci-ff-only.md

ci-ff-only.yml

Overall, this workflow achieves exactly the same as the ci-minimal._yml but it uses a few optimizations. Let's go through what is differet.

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Jobs

The workflow defines a single job named ci that runs on an Ubuntu environment.

jobs:
  ci:
    runs-on: ubuntu-latest

Steps

The ci job consists of several steps that are executed sequentially:

Get default target branch name

This step is added - the step has an id, and the step sets an output-parameter. This is how GitHub Actions enables steps to share information between one and another.

When a step has an id, and sets and output, other steps can access that using

${{ steps.<step_id>.outputs.<output_name> }}

- name: Get default target branch name
  id: repo
  run: |
    set -ex
    TARGET_BRANCH=$( gh repo view --json defaultBranchRef --jq .defaultBranchRef.name )
    echo ::set-output name=target_branch::$TARGET_BRANCH

Rebase Against Default Target Branch

This step does the same as before, only this time it doesn't execute the gh CLI command, it simply reuses the target_branch name retrived in the step before.

- name: Rebased against default target branch
  run: |
    set -ex
    git rebase ${ORIGIN}/${{ steps.repo.outputs.target_branch }}

Checkout default branch, merge only if Fast-Forward and Push back to origin

The previous flow simply pushed changes back to the defaould target branch. But now the step is updated to even handle any changes to the default branch that might have accurred during the time it toot kto veryfy the branch.

It checks out the target branch, updates with a pull, then merges the issue branch into it making sure that only Fast-Forward merges are allowed - and then pushes the result back to origin (GitHub). Last time we had re-executed the gh CLI command to get the repo's defaul tranch, but this time we simply reuse the information from the earlier step that retrived it once and for all.

- name: Checkout default branch, merge only if Fast-Forward and Push back to origin
  run: |
    set -ex
    git checkout ${{ steps.repo.outputs.target_branch }}
    git pull
    git merge --ff-only ${{github.ref_name}}
    git push ${ORIGIN} ${{ steps.repo.outputs.target_branch }}

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