Tab completion with cd and ls

[Keith Goodman]

Is it hard to modify the behavior of tab completion when a line starts
with a keyword like cd and ls?

Currently tab completion (for cd and ls) searches through directories,
octave commands, and variables. When using cd and ls it would be nice
if the octave commands and variables were not included in the search.

>> cd tmp/       [two tabs]
Display all 1994 possibilities? (y or n)

There's not much in my tmp directory; most of the 1994 positibilities
are Octave functions and variables.

>> cd oct         [two tabs]
octave_config_info        octave_core_file_name     octave_tmp_file_name
octave_core_file_limit    octave_core_file_options  octcvs/

In this case there is only one meaningful tab completion (cd octcvs/).