How push back some changes to Pull request?

[cawa-93]

I would like to create a workflow that would come into each PR and format the code according to the code style. On paper, it looks simple: pull PR, run formatting, push any changes.
My workflow:

on: [push, pull_request]

jobs:
  format:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
    
      - uses: actions/setup-node@v3
      - run: npm run format --if-present
      
      - run: |
          git config user.name github-actions
          git config user.email [email protected]
          git add --all
          git diff-index --quiet HEAD || git commit -m "style: format code"
          git push

And it works great for push events. However, I get an error in pull_request events:

[detached HEAD 36717a0] style: format code
 1 file changed, 1 insertion(+), 1 deletion(-)
fatal: You are not currently on a branch.
To push the history leading to the current (detached HEAD)
state now, use

    git push origin HEAD:<name-of-remote-branch>

Error: Process completed with exit code 128.

I don't understand what caused this error, and how should I initialize the workflow to be able to push changes back to PR

[motss]

Did you try git push origin HEAD:${{ github.head_ref }}?

[motss]

@cawa-93 I'd like to leave this comment here for future reference for all the folks who wants to commit then push changes directly to the working branch within Github Actions.

Key Takeaways:

1. Checkout with a defined ref:

   This is necessary because GitHub Actions checks out in detached HEAD mode, meaning it doesn’t check out your branch by default.

     uses: actions/checkout@v4
     with:
        ref: ${{ github.head_ref }}

2. Set Up Git with user.name and user.email:

   You can use the Github Actions bothttps://api.github.com/users/github-actions%5Bbot%5D, read here for more details.

   git config user.name "github-actions[bot]" # This is required for a git push
   git config user.email "41898282+github-actions[bot]@users.noreply.github.com" # This is required for a git push

Sample workflow

name: Push to PR

on:
  pull_request:
    branches:
      - '**'

jobs:
  push-to-pr:
    name: Push to PR
    runs-on: ${{ matrix.os }}
    strategy:
      matrix:
        os: [ubuntu-latest]

    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          ref: ${{ github.head_ref }} # Required

      - name: Setup Git # Required
        run: |
          git config user.name "github-actions[bot]"
          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"

      - name: Commit changes
        run: |
          echo 'test' > test.md
          git add .
          git commit -m 'chore: new change'
          git push