Packrat -> renv

Fixes hadley#960

rmarkdown-workflow.qmd

@@ -56,7 +56,7 @@ I've drawn on my own experiences and Colin Purrington's advice on lab notebooks
     That will let you fix any problems while the code is still fresh in your mind.
 
 -   If you want your code to be reproducible in the long-run (i.e. so you can come back to run it next month or next year), you'll need to track the versions of the packages that your code uses.
-    A rigorous approach is to use **packrat**, <http://rstudio.github.io/packrat/>, which stores packages in your project directory, or **checkpoint**, <https://github.com/RevolutionAnalytics/checkpoint>, which will reinstall packages available on a specified date.
+    A rigorous approach is to use **renv**, <https://rstudio.github.io/renv/index.html>, which stores packages in your project directory.
     A quick and dirty hack is to include a chunk that runs `sessionInfo()` --- that won't let you easily recreate your packages as they are today, but at least you'll know what they were.
 
 -   You are going to create many, many, many analysis notebooks over the course of your career.