Start on a Git-based review flow (#27103)

Release Notes:

- N/A

---------

Co-authored-by: Nathan Sobo <nathan@zed.dev>

crates/assistant_eval/src/eval.rs

@@ -82,7 +82,7 @@ impl Eval {
             assistant.update(cx, |assistant, cx| {
                 assistant.thread.update(cx, |thread, cx| {
                     let context = vec![];
-                    thread.insert_user_message(self.user_prompt.clone(), context, cx);
+                    thread.insert_user_message(self.user_prompt.clone(), context, None, cx);
                     thread.send_to_model(model, RequestKind::Chat, cx);
                 });
             })?;