Trying to set up a simple action (my first one) that uses the value of github.repository (so, e.g., user/repo). In my action.yaml I’ve tried passing as follows:

runs:
  using: 'docker'
  image: 'Dockerfile'
  args:
    - ${{ env.GITHUB_REPOSITORY }}

and also ${{ github.repository }} as the last line but both don’t work. I assume I haven’t understood contexts well enough yet. Could anyone please explain how to do this?
Thanks!