Bug: fish integration seems to limit the number of layers of autocompletion

[XaF]

Example:

1. Create the following directory structure:

   cmd/
      a/
         b/
            c/
               d/
                  e/
                     f.sh
   

   i.e. mkdir -p cmd/a/b/c/d/e && touch cmd/a/b/c/d/e/f.sh
2. Run chmod +x cmd/a/b/c/d/e/f.sh
3. Add the directory to your omnipath (ideally do this in a git repository): set -Ux OMNIPATH $PWD/cmd
4. Try omni autocompletion: omni a <tab>

This does autocomplete the b but does not seem to pursue after.
This seems similar with any other commands.

Omni does return the right autocompletion value (COMP_CWORD=2 omni --complete a returns b, COMP_CWORD=3 omni --complete a b returns c, etc.).

This works as expected on bash and zsh (i.e. autocomplete until omni a b c d e f), fish is the only one having a weird behavior.

[XaF]

@tminusplus since you're using fish, would be able to investigate what's happening / make a PR to fix the issue in the fish template?

@oefd I think you're using fish too?