Binderhub unable to access private repo with git-credential-env

Bug description

When running binderhub with repo2docker, binderhub is unable to clone from a private repo.

Expected behaviour

Binderhub should be able to clone from a private repo and start building the image.

Actual behaviour

How to reproduce

1. Deploy binderhub using 0.2.0-c8ab0a3 with repo2docker a251ad26 w/ a github access token
2. Try to create a new binder using a link to a private github repo
3. Build will fail with error above

Your personal set up

• OS: macOS 10.13.6
• Docker version: Docker version 18.09.2, build 6247962
• repo2docker version: image tag a251ad26
• binderhub version: 0.2.0-c8ab0a3

Github section of my secrets.yaml:

config:
  GitHubRepoProvider:
    access_token: ****

Access token has the proper permissions:

Workaround

I was able to narrow down the cause of the issue to a git install change in the Dockerfile: https://github.com/jupyter/repo2docker/commit/ee93bcf1a6155a71c8978b78b8bf03282dbdf088#diff-3254677a7917c6c01f55212f86c57fbf

I reverted this change to the Dockerfile (used python:3.7 instead of alpine) and built the image locally to use for my binderhub deployment and was able to successfully clone and build from a private github repo.

[eexwhyzee]

yeah that sounds good to me as well, I’ll have a PR out sometime today

[eexwhyzee]

@betatim alright i figured out what’s going on, the git-credential-env file requires bash, and the new repo2docker Dockerfile is based on alpine which doesn’t come with bash by default, I confirmed that adding bash installation to the existing Dockerfile fixes the bug (adds ~5MB to the image)