tramp-completion-file-name-regexp

tramp-completion-file-name-regexp is a variable defined in `tramp.el'.
Its value is

"\\`/[^/]*\\'"

• This variable may be risky if used as a file-local variable.

Documentation:
Regular expression matching file names handled by Tramp completion.
This regexp should match partial Tramp file names only.

Please note that the entry in `file-name-handler-alist' is made when
this file (tramp.el) is loaded. This means that this variable must be set
before loading tramp.el. Alternatively, `file-name-handler-alist' can be
updated after changing this variable.

Also see `tramp-file-name-structure'.