style: use strict-casts and strict-raw-types

analysis_options.yaml

@@ -1,6 +1,9 @@
 include: package:lints/recommended.yaml
 
 analyzer:
+  language:
+    strict-casts: true
+    strict-raw-types: true
   strong-mode:
     implicit-casts: false
     implicit-dynamic: false

lib/src/repository.dart

@@ -1000,7 +1000,7 @@ class Repository {
   /// values respectively.
   ///
   /// Throws a [LibGit2Error] if error occured.
-  List mergeAnalysis({
+  List<Object> mergeAnalysis({
     required Oid theirHead,
     String ourRef = 'HEAD',
   }) {