feat: compare函数增加返回diff

seecoder-gitlab-server/src/main/java/com/nju/edu/gitlab/service/impl/ProjectServiceImpl.java

@@ -138,6 +138,7 @@ public class ProjectServiceImpl implements ProjectService {
                 .newPath(diff.getNewPath())
                 .oldPath(diff.getOldPath())
                 .renamedFile(diff.getRenamedFile())
+                .diff(diff.getDiff())
                 .build()).collect(Collectors.toSet());
         return res;
     }