Add some RStudio Cloud specifics

[jennybc]

Summarizing discussion in https://github.com/jennybc/happy-git-with-r/pull/166

"New Project" unfolds differently in Cloud. Only available from the page where you get an overview of your Projects. Not obviously available once you have entered a Project.

Auth considerations:

... the "New Project from Git Repository" workflow in RSC won't work with SSH key authentication, since the keys don't persist across projects in RSC. So the only option is HTTPS + PATs.

I have a question for you @debbieyuster (and probably also @mine-cetinkaya-rundel). Do PATs persist in RStudio Cloud? Has either of you written up your credential advice for students on RStudio Cloud? My impression is that Cloud users basically have to follow the Happy Git advice for linux users.

[debbieyuster]

I thought the answer was no and just tested it out again to confirm. No, PATs do not persist across projects in RStudio Cloud and neither does the .Renviron file. So the Happy Git advice for Linux users won't suffice. I have some advice written but it might make you wince: my students keep their PATs somewhere handy and just copy/paste it each time they are prompted.

[jennybc]

I have no hope of PATs travelling across Projects on Cloud. More realistic is configuring a PAT to persist over time within a Cloud Project. That's where I suspect the Cloud advice is basically the default advice for a linux user (except, of course, they have to follow it once-per-Project).