Support token-based Git authentication

`auto-changelog` assumes the Git client is authenticated to perform actions like checking the tags for updating the changelog. We should consider adding support for token-based authentication to support `persist-credentials: false` in [`actions/checkout`](https://github.com/actions/checkout).

Start by tracing how auto-changelog invokes Git to inspect tags during changelog updates, then review the linked actions/checkout behavior when persist-credentials is false. Done means the utility can perform those Git operations with token-based authentication in that workflow, with coverage for the supported authentication path.

Written by the indexing model from the issue text.