fix fish completions with words containing -f

[azarmadr]

Fixes #2686

[azarmadr]

It is a small change. only adding a regex to filter out -f in between words

[casey]

I switched to using Clap's dynamic completion engine in #3167. The new completion engine calls into the just binary to get completions. This allows us to implement custom completion logic in Rust for all supported shells, instead of having to patch in support for each individual shell.

I created #2406 to track improvements to the new completion engine in one place.

I think this should work with the new engine.