Github Mirror is a GitHub Action that keeps a GitHub repository up to date as a mirror of an external repository. It will synchronize all branches and commits from the specified repository, it will not copy non-Git data such as Pull Requests.

To create a mirror, start by creating a repository locally and creating a branch to hold the workflow file. The branch should be named such that it will not conflict with a branch name in the source repository.

$ gh repo create --public --confirm mirror
$ git -C mirror checkout -b __mirror
$ mkdir -p mirror/.github/workflows

Create a file like the one below in your repository. Replace TARGET_REPO_HERE with the URL of a the git repository to mirror.

# .github/workflows/mirror.yml
name: 'mirror'
on:
  push:
    branches:
        - __mirror
  schedule:
    - cron: '* 3 * * *'
  workflow_dispatch:

jobs:
  mirror:
    runs-on: ubuntu-latest
    name: mirror
    steps:
      - name: mirror
        id: mirror
        uses: bridgelightcloud/github-mirror-action@v1
        with:
          origin: 'TARGET_REPO_HERE'
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

Commit and push your changes

$ git -C mirror add .
$ git -C mirror commit -am 'Add mirror workflow'
$ git -C mirror push -u origin __mirror

The workflow will start immediately and copy the source repository. The workflow will continue to run on the schedule specified on the cron line (in the example above, 3 AM UTC every day).

The code is trivial, as such this repository is licensed under the Creative Commons CC-0 license.