complete: improvements for the --hyperlink-format flag

The goal is to make the completion for `rg --hyperlink-format v<TAB>`
work in the fish shell.

These are not exhaustive (the user can also specify custom formats).
This is somewhat unfortunate, but is probably better than not doing
anything at all.

The `grep+` value necessitated a change to a test.

Closes #3096

crates/core/flags/defs.rs

@@ -3008,6 +3008,19 @@ https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda
         &DOC
     }
 
+    fn doc_choices(&self) -> &'static [&'static str] {
+        static CHOICES: LazyLock<Vec<String>> = LazyLock::new(|| {
+            let mut aliases = grep::printer::hyperlink_aliases();
+            aliases.sort_by_key(|alias| {
+                alias.display_priority().unwrap_or(i16::MAX)
+            });
+            aliases.iter().map(|alias| alias.name().to_string()).collect()
+        });
+        static BORROWED: LazyLock<Vec<&'static str>> =
+            LazyLock::new(|| CHOICES.iter().map(|name| &**name).collect());
+        &*BORROWED
+    }
+
     fn update(&self, v: FlagValue, args: &mut LowArgs) -> anyhow::Result<()> {
         let v = v.unwrap_value();
         let string = convert::str(&v)?;
@@ -7724,9 +7737,10 @@ mod tests {
                 assert!(
                     choice.chars().all(|c| c.is_ascii_alphanumeric()
                         || c == '-'
-                        || c == ':'),
+                        || c == ':'
+                        || c == '+'),
                     "choice '{choice}' for flag '{long}' does not match \
-                     ^[-:0-9A-Za-z]+$",
+                     ^[-+:0-9A-Za-z]+$",
                 )
             }
         }