complete/zsh: improve --hyperlink-format completion

Also don't re-define helper functions if they exist.

Closes #3102

crates/core/flags/complete/zsh.rs

@@ -19,5 +19,14 @@ long as it meets criteria 3 and 4 above.
 
 /// Generate completions for zsh.
 pub(crate) fn generate() -> String {
-    include_str!("rg.zsh").replace("!ENCODINGS!", super::ENCODINGS.trim_end())
+    let hyperlink_alias_descriptions = grep::printer::hyperlink_aliases()
+        .iter()
+        .map(|alias| {
+            format!(r#"    {}:"{}""#, alias.name(), alias.description())
+        })
+        .collect::<Vec<String>>()
+        .join("\n");
+    include_str!("rg.zsh")
+        .replace("!ENCODINGS!", super::ENCODINGS.trim_end())
+        .replace("!HYPERLINK_ALIASES!", &hyperlink_alias_descriptions)
 }