Xcode merge branch,remind tree conflict when add some new file

I create a branch2 and add some new class file,when i merge into master branch,Xcode reminds us:“The files ViewModel.h,ViewModel.m had a tree conflict”
If I just edit some code but not add new file,it will be ok,but how should i solve this problem?

Git Baby is a git and github fan, let's start git clone.