provide good docker image for pkg devel

[maxheld83]

currently, ghactions (and all R actions contained therein) require that the user bring her own docker image, such as rocker/tidyverse, or whatever really.
This makes some sense for random rmd projects (etc.), where the compute environment might well be arbitrary.

It makes a lot less sense for CRAN-bound pkg-dev, where we're usually targeting a pretty well-defined compute environment (CRAN checks)

So it might make sense to default to / standardise on one docker image to run some of the pkg dev actions in. (And this is what the current focus of the project is).

The question is which image (in order of my descending, gut-feeling preference):

1. one of the r-hub images, because these are (AFAIK?) closely replicating CRAN environments, are pretty slim and are concerned with pkg dev.
2. One of the rocker images rocker/r-ver.
3. One of the images maintained by RStudio as part of shinyapps.io or those used in rstudio launcher? (rely on rstudio images, as those used for rstudio launcher #96). (I know zilch about those).

@jimhester so my suggestion would be:

• default to the r-hub images
• ask you, or the slack channel which is most suitable.

This would imply:

• We limit ghactions to one computing environment (say, debian), and leave the multi-platform testing to r-hub, for now.
• We limit ghactions to one r version (say, release), and again, leave the multi-version testing to r-hub.
• (We might later add an action to run multiple tests on r-hub as per add action for r-hub #71, but maybe not for every commit, but only on release candidates, or triggered by a special commit message or whatever, with all the results from r-hub pasted below the commit or PR).

[maxheld83]

naturally, this wouldn't apply for some of the "later" actions, such as styler::style_pkg()as in #103, because these can run on pretty much any well-suited docker image we like.

[jimhester]

I am not sure the RStudio ones actually exist currently, so I think relying on the R-hub ones seems like the best plan in the short term.

[maxheld83]

ubuntu-gcc-release it is.

[maxheld83]

talked with **** (RStudio employee) yesterday and s/he suggested to take a look at

• rstudio base img (which does some cool things) (this is open)
• imgs used in launcher (apparently open)
• and especially: imgs used for linux pkg building in rspm (apparently open)

Mariana-trench deep backlog, my favorite place for issues.

[jimhester]

The repo is here FWIW https://github.com/rstudio/r-docker, they are versioned by OS and R version, so you can use rstudio/r-base:3.5-xenial for R 3.5 on xenial etc.