Add batch script files and enhance git staging logic

- Introduced 20 new batch script files (BatchScript01.luau to BatchScript20.luau) for testing purposes.
- Enhanced the `change_processor` to consolidate git staging operations, reducing the risk of index.lock races by batching paths for staging.
- Updated the `PatchSet` struct to include a new field for pre-resolved filesystem paths to stage via git add.
- Modified the API to handle batch staging more efficiently, ensuring all files are staged correctly in mixed write scenarios.

These changes improve the testing framework and optimize git integration for batch operations.

tests/tests/git_sync_defaults.rs

@@ -690,3 +690,212 @@ fn init_style_script_staging_targets_init_file() {
         );
     }
 }
+
+// ===========================================================================
+// Batch staging: many files in a single write request
+// ===========================================================================
+
+const BATCH_SCRIPT_COUNT: usize = 20;
+
+fn batch_script_name(i: usize) -> String {
+    format!("BatchScript{:02}", i)
+}
+
+fn batch_script_rel_path(i: usize) -> String {
+    format!("src/{}.luau", batch_script_name(i))
+}
+
+#[test]
+fn batch_stage_20_files_no_index_lock_race() {
+    let mut session = TestServeSession::new_with_git("git_sync_defaults", |path| {
+        git_commit_all(path, "initial commit");
+        for i in 1..=BATCH_SCRIPT_COUNT {
+            fs::write(
+                path.join(batch_script_rel_path(i)),
+                format!("-- modified {}\nreturn {{}}\n", i),
+            )
+            .unwrap();
+        }
+    });
+    let info = session.wait_to_come_online();
+    let read = session.get_api_read(info.root_instance_id).unwrap();
+
+    let mut stage_ids = Vec::new();
+    for i in 1..=BATCH_SCRIPT_COUNT {
+        if let Some((id, _)) = find_instance_by_name(&read.instances, &batch_script_name(i)) {
+            stage_ids.push(id);
+        }
+    }
+    assert!(
+        stage_ids.len() >= BATCH_SCRIPT_COUNT,
+        "Should find all {} batch scripts, found {}",
+        BATCH_SCRIPT_COUNT,
+        stage_ids.len()
+    );
+
+    let write_request = WriteRequest {
+        session_id: info.session_id,
+        removed: vec![],
+        added: HashMap::new(),
+        updated: vec![],
+        stage_ids,
+    };
+    session.post_api_write(&write_request).unwrap();
+    thread::sleep(Duration::from_millis(1500));
+
+    for i in 1..=BATCH_SCRIPT_COUNT {
+        assert!(
+            git_is_staged(session.path(), &batch_script_rel_path(i)),
+            "{} should be staged",
+            batch_script_name(i)
+        );
+    }
+}
+
+#[test]
+fn batch_source_write_20_files_all_staged() {
+    let mut session = TestServeSession::new_with_git("git_sync_defaults", |path| {
+        git_commit_all(path, "initial commit");
+    });
+    let info = session.wait_to_come_online();
+    let read = session.get_api_read(info.root_instance_id).unwrap();
+
+    let mut updates = Vec::new();
+    let mut stage_ids = Vec::new();
+    for i in 1..=BATCH_SCRIPT_COUNT {
+        if let Some((id, _)) = find_instance_by_name(&read.instances, &batch_script_name(i)) {
+            let mut props = UstrMap::default();
+            props.insert(
+                ustr("Source"),
+                Some(Variant::String(format!(
+                    "-- batch pull {}\nreturn {{}}\n",
+                    i
+                ))),
+            );
+            updates.push(InstanceUpdate {
+                id,
+                changed_name: None,
+                changed_class_name: None,
+                changed_properties: props,
+                changed_metadata: None,
+            });
+            stage_ids.push(id);
+        }
+    }
+    assert!(
+        updates.len() >= BATCH_SCRIPT_COUNT,
+        "Should find all {} batch scripts, found {}",
+        BATCH_SCRIPT_COUNT,
+        updates.len()
+    );
+
+    let write_request = WriteRequest {
+        session_id: info.session_id,
+        removed: vec![],
+        added: HashMap::new(),
+        updated: updates,
+        stage_ids,
+    };
+    session.post_api_write(&write_request).unwrap();
+    thread::sleep(Duration::from_millis(2000));
+
+    for i in 1..=BATCH_SCRIPT_COUNT {
+        let rel = batch_script_rel_path(i);
+        assert!(
+            git_is_staged(session.path(), &rel),
+            "{} should be staged after batch Source write",
+            batch_script_name(i)
+        );
+        let content = fs::read_to_string(session.path().join(&rel)).unwrap();
+        assert!(
+            content.contains(&format!("batch pull {}", i)),
+            "{} should have new content on disk",
+            batch_script_name(i)
+        );
+    }
+}
+
+#[test]
+fn batch_mixed_stage_and_source_write() {
+    let mut session = TestServeSession::new_with_git("git_sync_defaults", |path| {
+        git_commit_all(path, "initial commit");
+        // Modify the first 10 files on disk (push-accepted: already on disk, just stage)
+        for i in 1..=10 {
+            fs::write(
+                path.join(batch_script_rel_path(i)),
+                format!("-- push modified {}\nreturn {{}}\n", i),
+            )
+            .unwrap();
+        }
+    });
+    let info = session.wait_to_come_online();
+    let read = session.get_api_read(info.root_instance_id).unwrap();
+
+    let mut updates = Vec::new();
+    let mut stage_ids = Vec::new();
+
+    // Files 1-10: push-accepted (already modified on disk, just stage)
+    for i in 1..=10 {
+        if let Some((id, _)) = find_instance_by_name(&read.instances, &batch_script_name(i)) {
+            stage_ids.push(id);
+        }
+    }
+
+    // Files 11-20: pull-accepted (Source write + stage)
+    for i in 11..=BATCH_SCRIPT_COUNT {
+        if let Some((id, _)) = find_instance_by_name(&read.instances, &batch_script_name(i)) {
+            let mut props = UstrMap::default();
+            props.insert(
+                ustr("Source"),
+                Some(Variant::String(format!(
+                    "-- pull source {}\nreturn {{}}\n",
+                    i
+                ))),
+            );
+            updates.push(InstanceUpdate {
+                id,
+                changed_name: None,
+                changed_class_name: None,
+                changed_properties: props,
+                changed_metadata: None,
+            });
+            stage_ids.push(id);
+        }
+    }
+
+    assert!(
+        stage_ids.len() >= BATCH_SCRIPT_COUNT,
+        "Should have {} stage_ids, got {}",
+        BATCH_SCRIPT_COUNT,
+        stage_ids.len()
+    );
+
+    let write_request = WriteRequest {
+        session_id: info.session_id,
+        removed: vec![],
+        added: HashMap::new(),
+        updated: updates,
+        stage_ids,
+    };
+    session.post_api_write(&write_request).unwrap();
+    thread::sleep(Duration::from_millis(2000));
+
+    // All 20 files should be staged
+    for i in 1..=BATCH_SCRIPT_COUNT {
+        assert!(
+            git_is_staged(session.path(), &batch_script_rel_path(i)),
+            "{} should be staged in mixed batch",
+            batch_script_name(i)
+        );
+    }
+
+    // Files 11-20 should have the new pull content
+    for i in 11..=BATCH_SCRIPT_COUNT {
+        let content = fs::read_to_string(session.path().join(batch_script_rel_path(i))).unwrap();
+        assert!(
+            content.contains(&format!("pull source {}", i)),
+            "{} should have pull content on disk",
+            batch_script_name(i)
+        );
+    }
+}