github 2fa breaks publishing-outputs tutorial

[caraka]

This is more a feature request than a bug. If you have 2fa enabled on your github account, you use an api key rather than a traditional private key to authenticate.

7 resource-gist errored resource script '/opt/resource/check []' failed: exit status 1 stderr: Error loading key "/tmp/git-resource-private-key": invalid format

If it is easy enough to alter the format checking that happens somewhere in starkandwayne/concourse to allow this variation, all good. (This may also require the user to edit git credentials in bump-timestamp-file.sh as well.) If not, a note about this limitation on the tutorial page would be useful. :cue complaints about inputting api keys