Credentials in additional_netrc_lines are not used for repin

[peakschris]

We specify credentials for a private repo in additional_netrc_lines. These work for regular fetch. But they are not passed to coursier for repin operations.

Setting COURSIER_CREDENTIALS="repo user:pass" envvar prior to repin is a workaround. However, since the credentials are already in additional_netrc_lines, it seems a shame not to use them automatically.

This is windows. I am not sure if the issue is windows specific.