.Rbuildignore.Rbuildignore has a regular expression on each line, but it's
usually easier to work with specific file names. By default,
use_build_ignore will (crudely) turn a filename into a regular
expression that will only match that path. Repeated entries will be
silently removed.
use_build_ignore(files, escape = TRUE)Character vector of path names.
If TRUE, the default, will escape . to
\. and surround with ^ and $.