Return a list of the files to be processed in a directory. We know that
this directory doesn’t have a .document file, so we’re looking for
real files. However we may well contain subdirectories which must be tested
for .document files.
# File lib/rdoc/rdoc.rb, line 329
def list_files_in_directory dir
files = Dir.glob File.join(dir, "*")
normalized_file_list files, false, @options.exclude
end