Tramp hostname and username completion (Fixed on Emacs 29)

NOTE: On Emacs 29.2 and Tramp 2.7 the workarounds described in this section are not necessary anymore, since the relevant completion tables have been fixed.

In combination with Orderless or other non-prefix completion styles like ‘substring’ or ‘flex’, host names and user names are not made available for completion after entering ‘/ssh:’. In order to avoid this problem, the ‘basic’ completion style should be specified for the file completion category, such that ‘basic’ is tried before ‘orderless’. This can be achieved by putting ‘basic’ first in the completion style overrides for the file completion category.

(setq completion-styles '(orderless basic)
      completion-category-defaults nil
      completion-category-overrides '((file (styles basic partial-completion))))