This facilitates a legitimate use-case for browserless systems. From the
README:
> On systems without a web browser, set the -device flag to authenticate
> on another device using [OAuth device flow]:
> ```ini
[credential]
helper = cache --timeout 7200 # two hours
helper = oauth -device
```
[OAuth device flow]: https://www.rfc-editor.org/rfc/rfc8628
Please note that, for the documentation about the man-page to be
accurate, https://github.com/NixOS/nixpkgs/pull/302922 must be merged.
