class walk_method : [ `Dir of string | `File of string | `Stay ] -> ftp_method
This FTP method walks to the target directory:
`File name: The name is interpreted as slash-separated path.
It is always interpreted relative to the home directory of the
user (i.e. the directory after login), even if it begins with a
slash. The FTP command walks to the directory containing name.
`Dir name: The FTP command walks to the directory name (same
syntax as for `File).
`Stay: The FTP command does nothing (stays in the current directory).