The method will look for source code files (recursively or not) that
  match known filename extensions. Each found source code file is
  then source()d.
If the search is recursive, subdirectories are entered if and only if
  either (1) the name of the subdirectory is the same as a loaded
  (and installed) package, or (2) if there is no installed package
  with that name. The latter allows common code to be organized in
  directories although it is still not assigned to packages.
Each of the directories given by argument paths will be
  processed one by one. This makes it possible to have more than one
  file tree containing patches.
To set an options, see options(). To set a system
  environment, see Sys.setenv().
  The character ; is interpreted as a separator. Due to
  incompatibility with Windows pathnames, : is not a
  valid separator.