create_file_for_arg
Description:
Creates a File corresponding to a filename that was given as part of the invocation of this.
This differs from new_for_commandline_arg in that it resolves relative pathnames using the current working directory of the invoking process rather than the local process.
Parameters:
| this | |
| arg | 
           an argument from this  | 
      
Returns:
| 
           a new File  |