Error: Error: Command failed: git push heroku HEAD:refs/heads/main --force

Below is the error I received:

And this is my main.yml file:

name: Deploy

on:
  push:
    branches:
      - master

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Install packages
        run: npm install
      - name: Build project
        run: npm run-script build
      - uses: akhileshns/heroku-deploy@v3.11.10 # This is the action
        with:
          heroku_api_key: ${{secrets.HEROKU_API_KEY}}
          heroku_app_name: "git-auto" #Must be unique in Heroku
          heroku_email: "[e-mail]"
          procfile: "web: npm start"

[IshaanOhri]

So I figured out the exact problem and the exact solution for this. If we connect the repository on Heroku for automatic deployments, then what happens is that as soon as a commit is pushed, the repository content on Heroku changes and the GitHub Action is also triggered, which makes use of the repository content on Heroku, makes some changes to it and pushes it back to Heroku. In between the GitHub action accessing the Heroku content and pushing it back to Heroku, the content on Heroku changes due to automatic deployment which causes differences in the content, because of which this error arises.

The solution to this is to not enable the automatic deployment on Heroku.

I really feel this is worth mentioning as an important note in the README, therefore I have made the required changes and have generated a PR for the same. Would appreciate merging the PR and closing the issue.

[IshaanOhri]

Thanks for providing the correct information. That was the probable explanation I could think of. My bad. But yeah, the problem was related to Automatic Deployments. Thanks, man!