Sets (if create = TRUE) or gets the cache
directory associated with the Require package.
cacheDir(create, verbose = getOption("Require.verbose"))cachePkgDir(create)
If !is.null(cacheGetOptionCachePkgDir()), i.e., a cache path exists,
the cache directory will be created,
with a README placed in the folder. Otherwise, this function will just
return the path of what the cache directory would be.
A logical indicating whether the path should
be created if it does not exist. Default is FALSE.
Numeric or logical indicating how verbose should the function
be. If -1 or -2, then as little verbosity as possible. If 0 or FALSE,
then minimal outputs; if 1 or TRUE, more outputs; 2 even more. NOTE: in
Require function, when verbose >= 2, also returns details as if
returnDetails = TRUE (for backwards compatibility).
To set a different directory than the default, set the system variable:
R_USER_CACHE_DIR = "somePath" and/or R_REQUIRE_PKG_CACHE = "somePath"
e.g., in .Renviron file or Sys.setenv(). See Note below.