knitr::purl(), setting the chunk option purl to TRUE if it's not
already set to a literal value.This function is only exported for use in hook scripts, but it's not intended to be called by the end-user directly.
robust_purl(path)The path to the file you want to knitr::purl().
Other hook script helpers: 
diff_requires_run_roxygenize(),
dirs_R.cache(),
may_require_permanent_cache(),
precommit_docopt(),
roxygen_assert_additional_dependencies(),
roxygenize_with_cache()