complete/fish: Fix syntax for negated options

And also, negated options don't take arguments.

Specifically, the fish completion generator currently forgets to add
`-l` to negation options, leading to a list of these errors:

    complete: too many arguments

    ~/.config/fish/completions/rg.fish (line 146):
    complete -c rg -n '__fish_use_subcommand'  no-sort-files -d '(DEPRECATED) Sort results by file path.'
    ^
    from sourcing file ~/.config/fish/completions/rg.fish

    (Type 'help complete' for related documentation)

To reproduce, run `fish -c 'rg --generate=complete-fish | source'`.

It also potentially suggests a list of choices for negation options,
even though those never take arguments. That case doesn't occur with
any of the current options but it's an easy fix.

Fixes #2659, Closes #2655

crates/core/flags/complete/fish.rs

@@ -35,10 +35,11 @@ pub(crate) fn generate() -> String {
                 .replace("!DOC!", &doc),
         );
         if let Some(negated) = flag.name_negated() {
+            let long = format!("-l '{}'", negated.replace("'", "\\'"));
             out.push_str(
-                &template
+                &TEMPLATE
                     .replace("!SHORT!", "")
-                    .replace("!LONG!", &negated)
+                    .replace("!LONG!", &long)
                     .replace("!DOC!", &doc),
             );
         }