create_from_github should not assume authentication.

[cboettig]

Minor issue from #109

Currently, create_from_github() will throw an opaque error if the user has not put a valid GITHUB_PAT environmental variable, since without authentication the API will not return a permissions chunk. If any behavior doesn't need auth, then it should work without this, otherwise, it should be documented that you should set GITHUB_PAT as an env var, and the function should probably have an argument to specify the token directly, consistent with use_github() etc.

[jennybc]

reprex

library(withr)
library(devtools)
library(usethis)

with_envvar(
  new = c(GITHUB_PAT = NA, GITHUB_TOKEN = NA),
  code = create_from_github("r-lib/usethis", path = tempdir())
)
#> Error in !repo_info$permissions$push: invalid argument type

Created on 2017-12-26 by the reprex package (v0.1.1.9000).

[jennybc]

I think the idea is you are supposed to say fork = FALSE in this case, but I agree we have some flow/UI problems in this function (for example, the project created below is NOT, in fact, being opened in a new RStudio instance).

library(withr)
library(devtools)
library(usethis)

with_envvar(
  new = c(GITHUB_PAT = NA, GITHUB_TOKEN = NA),
  code = create_from_github("r-lib/usethis", path = tempdir(), fork = FALSE)
)
#> ✔ Cloning repo
#> ✔ Opening project in new RStudio instance

Created on 2017-12-26 by the reprex package (v0.1.1.9000).

[jennybc]

I renamed this issue to reflect what I can actually fix in this release. Everything else was moved into #214 (GitHub connectivity) and #215 (create_from_github() should share many arguments with use_github()).