The 'filenames' option to complete is removed, as it would prevent
proper completion of local refs like tmz/f13.

On systems with bash-completion >= 1.2, this should have little effect
because the _filedir command sets the option as needed (or emulates it
on older bash releases that lack compopt).

On systems with older bash-completion (like EL-5 currently), there is a
minor downside in that filename completion won't append trailing slashes
to directories without the 'filenames' option. Ideally, bash-completion
will be updated on EL-5 and this minor inconvenience will vanish