tramp-completion-mode

tramp-completion-mode is a variable defined in `tramp.el'.
Its value is

nil

Documentation:
If non-nil, external packages signal that they are in file name completion.

This is necessary, because Tramp uses a heuristic depending on last
input event. This fails when external packages use other characters
but , or ?\? for file name completion. This variable
should never be set globally, the intention is to let-bind it.