Only use fuzzy option completion if there is a leading -

Commit b768b9d3f (Use fuzzy subsequence completion for options names as well,
2024-01-27) allowed completing "oa" to "--foobar", which is a false positive,
especially because it hides other valid completions of non-option arguments.
Let's at least require a leading dash again before completing option names.

src/complete.rs

@@ -1435,6 +1435,9 @@ fn complete_param_for_command(
                 if whole_opt.len() < s.len() {
                     continue;
                 }
+                if !s.starts_with("-") {
+                    continue;
+                }
                 let anchor_start = !self.flags.fuzzy_match;
                 let Some(r#match) = string_fuzzy_match_string(s, &whole_opt, anchor_start) else {
                     continue;

tests/checks/complete.fish

@@ -601,3 +601,5 @@ complete -C'complete_long_option --slo'
 complete complete_long_option -f -o an-old-option
 complete -C'complete_long_option -ao'
 # CHECK: -an-old-option
+# But only if the user typed a dash
+complete -C'complete_long_option lo'