This function writes the language (in this case R) and a date from which packages will be downloaded from MRAN. The file is written to a hidden folder called `.binder/`.
Path to project
Version of R to lock down.
Date you need R to lock down to. By default it picks the most recent date a file was touched in this project but you can override this by specifying this explicitly. Date must be in ISO 8601 format, e.g. 2019-06-27