GitHub Action to combine multiple PRs into a single one

GitHub uses this Action to combine multiple dependabot PRs into a single one. Rather than having to deploy each PR individually, we can run this Action on a cron or workflow_dispatch to combine all the PRs into a single one to make dependency management just a little bit easier.

This Action is customizable so you can use it for your own purposes and it doesn't have to be specific to dependabot PRs.

Here is a PR example of this Action:

The Action ran on a cron, looked for all branches that had the dependabot prefix and then combined them into a single PR. Three pull requests were successfully combined and one was left out due to merge conflicts.

This allows us to deploy all the dependency updates at once rather than having to deploy each one individually.

Here is a brief example of how to use this Action in a workflow:

name: Combine PRs

on:
  schedule:
    - cron: '0 1 * * 3' # Wednesday at 01:00
  workflow_dispatch: # allows you to manually trigger the workflow

jobs:
  combine-prs:
    runs-on: ubuntu-latest

    steps:
      - name: combine-prs
        id: combine-prs
        uses: github/combine-prs@vX.X.X # where X.X.X is the latest version

By default, this Action uses the branch_prefix option set to dependabot to match the branches to combine. However, you can also use the branch_regex option to match branches using a regex pattern. This is useful if you want to match branches that don't have a specific prefix.

branch_regex is a string representing a regex pattern

If branch_regex is set, branch_prefix will be ignored.

If you need CI to re-run on your newly created "combined" PR, you'll need to use a token that has write access to your repository. This is because the default github.token that is provided to Actions prevents CI from running on new commits to prevent recursive workflows. You can use a personal access token or a GitHub App token to get around this.

- name: combine-prs
  id: combine-prs
  uses: github/combine-prs@vX.X.X # where X.X.X is the latest version
  with:
    github_token: ${{ secrets.PAT }} # where PAT is a GitHub Action's secret containing a personal access token

Alternatively, you can use a GitHub App token. This is the recommended approach as it is more secure than a personal access token and a lot more scalable for large organizations. The following open source Action helps to generate a GitHub App token for you which can then be passed into the combine-prs Action.

Here is an example doing exactly that:

name: Combine PRs

on:
  schedule:
    - cron: '0 1 * * 3' # Wednesday at 01:00
  workflow_dispatch:

jobs:
  combine-prs:
    runs-on: ubuntu-latest

    steps:
      - name: Use GitHub App Token
        uses: wow-actions/use-app-token@d7957e08172ca2e8e49b35b8d266ad585885edc7 # pin@v2.0.2
        id: generate_token
        with:
          app_id: ${{ secrets.APP_ID }} # The ID of the GitHub App
          private_key: ${{ secrets.PRIVATE_KEY }} # The private key of the GitHub App
          fallback: ${{ secrets.GITHUB_TOKEN }} # fall back to the default token if the app token is not available

      - name: combine-prs
        uses: github/combine-prs@vX.X.X # where X.X.X is the latest version
        with:
          github_token: ${{ steps.generate_token.outputs.BOT_TOKEN }} # A GitHub app token generated by the previous step

If you go the GitHub App route, it will need the following permissions:

• Commit statuses: Read-only
• Contents: Read and write
• Metadata: Read-only
• Pull requests: Read and write