Add comment about how r_version is determined
MODIFY
repo2docker/buildpacks/r.py
repo2docker/buildpacks/r.py
@@ -79,6 +79,8 @@ class RBuildPack(PythonBuildPack):
if not hasattr(self, "_r_version"):
parts = self.runtime.split("-")
+ # If runtime.txt is not set, or if it isn't of the form r-<version>-<yyyy>-<mm>-<dd>,
+ # we don't use any of it in determining r version and just use the default
if len(parts) == 5:
r_version = parts[1]
# For versions of form x.y, we want to explicitly provide x.y.z - latest patchlevel

Add comment about how r_version is determined