Problems checking out source code from within container:

1. container doesn't have permission to invoke the usual github actions/checkout@v3 Proposed workaround is to have container run with same UID as github runner; I haven't tried to pursue that.
2. should be able to share resources between jobs/steps using volumes and/or artifacts This seems pretty fussy just to check out some code.
3. Instead added git to docker container, then run checkout directly. Complications:
   • need to introduce a personal access token. don't want to use GIT_TOKEN, since that only works for attached repo; we know we want to pull from multiple repos (e.g. see workflow for github.com:rconybea/reflect). See GIT_ACCESS_TOKEN in .github/workflows/main.yml
   • git running inside container gives confusing error when it attempts checkout:

     fatal: unable to access 'https://github.com/rconybea/docker-action-example3.git/': OpenSSL/3.0.8: error:16000069:STORE routines::unregistered scheme
     

     This error is misleading - actual problem is that for some reason container doesn't recognize github.com's certificate. Wishfully added nixpkgs.cacert, to no visible effect. Successfully suppressed error by prefixing git commands with GIT_SSL_NO_VERIFY=true