Refactor git repository initialization and enhance logging levels

- Updated the `flatten_tree` function in `git.rs` to clarify the repository parameter name.
- Changed logging level from `debug` to `trace` in `finalize_patch_application` for more detailed output.
- Modified the `TestServeSession` initialization to persist git configuration to disk, ensuring user identity is accessible for subsequent operations.

These changes aim to improve code clarity, enhance logging detail, and ensure proper git configuration handling in tests.

tests/rojo_test/serve_util.rs

@@ -202,18 +202,16 @@ impl TestServeSession {
         copy_recursive(&source_path, &project_path)
             .expect("Couldn't copy project to temporary directory");
 
-        // Initialize git repo and run setup callback
-        let mut repo = gix::init(&project_path).expect("gix init failed");
-        {
-            let mut config = repo.config_snapshot_mut();
-            config
-                .set_raw_value(&gix::config::tree::User::NAME, "Test")
-                .unwrap();
-            config
-                .set_raw_value(&gix::config::tree::User::EMAIL, "test@test.com")
-                .unwrap();
-            let _ = config.commit_auto_rollback().unwrap();
-        }
+        // Initialize git repo and persist config to disk so that
+        // git_add_all_and_commit (which opens a fresh gix handle via
+        // gix::discover) can read user identity. The gix SnapshotMut
+        // API is in-memory only and never writes to .git/config.
+        gix::init(&project_path).expect("gix init failed");
+        fs::write(
+            project_path.join(".git/config"),
+            "[user]\n\tname = Test\n\temail = test@test.com\n[core]\n\tautocrlf = false\n",
+        )
+        .expect("Failed to write .git/config");
 
         setup(&project_path);