`includeRmd` should evaluate chunks in a child of global

[lionel-]

Currently the Rmd is evaluated in a child of the roxygen namespace.

[hadley]

@lionel- can you please confirm this fixes your issue, since I didn't write a unit test.

[lionel-]

It works, thanks!

r-lib/tidyselect@31840e9#diff-f1aa839ea4153e9942f4481ce2eb65a3L22

[lionel-]

One issue with evaluating in a child of global is that closures and quosures are marked with non-default environments and that is a bit distracting in user documentation. Also this makes it more difficult to define S3 methods since tidyverse S3 dispatch (purrr, vctrs) doesn't inspect the calling env, only the global env.

On the other hand evaluating in global would cause more issues of state cleanup (cf #1092).

[lionel-]

a bit distracting in user documentation

The local env adresses also cause spurious diffs.