HTTPS authentication with GitHub will require a Personal Accesss Token

https://github.blog/2020-12-15-token-authentication-requirements-for-git-operations/

It's unclear to me what the best course of action is. Some thoughts:

• We already use the OAuth flow to authenticate with the GitHub API with wflow_use_github() when creating a new GitHub repository. But this is a one-time operation, and the token is purposefully immediately discarded (so that there is no security leak). If we update wflow_git_push()/wflow_git_pull() to use the OAuth flow, this would get tedious. And for security reasons, I don't really want workflowr to venture into managing tokens.

• git2r has a work-in-progress PR https://github.com/ropensci/git2r/pull/422 to use the credentials package. This would enable git2r to access the same PAT used by command-line Git. This would be convenient, but we'd still need a way for users to create the PAT in the first place. Many workflowr users are first-time Git users, so we can't assume they already have a PAT available. The usethis package has an entire vignette on GitHub authentication. Their current instructions are 1) create a PAT with usethis::create_github_token() (unfortunately this is a manual step, it only opens the browser to the page), 2) save the PAT to the Git credentials store with gitcreds::gitcreds_set(). I wish this could be more automated, but I'm not sure if that is possible (or advisable).

Review wflow_use_github(), wflow_git_push(), and wflow_git_pull() to understand the current OAuth and Git authentication paths. Read the linked git2r credentials work and the referenced usethis GitHub authentication vignette before deciding on the supported flow. Done requires an agreed approach for HTTPS authentication and documented behavior for first-time GitHub users.