##### PATH MANAGEMENT 
 
MyStack.push_paths :my_file_group, ["relative/path1", "relative/path2"], "**/*.rb"
MyStack.push_paths :my_file_group, "relative/path3"
 
MyStack.dirs_for :my_file_group           #=> MyStack.roots * [relative/path1, relative/path2, relative/path3]
MyStack.dirs_and_glob_for :my_file_group  #=> MyStack.roots * [relative/path1, **/*.rb]
                                          #=> MyStack.roots * [relative/path2, **/*.rb]
                                          #=> MyStack.roots * [relative/path3, nil]
 
MyStack.paths_for(:my_file_group)         # list of all files that match all roots * relative_paths * globs
MyStack.unique_paths_for(:my_file_group)  # like paths_for but will unique the files taking the last declared
 
MyStack.unique_paths_for(:my_file_group, :invert => true)