解决: 增加-m参数可以看到merge的修改
$ git log -p -m app/models/banners.py手册说明:
-mThis flag makes the merge commits show the full diff like regular commits; for each merge parent, a separate log entry and diff is generated. An exception is that only diff against the first parent isshown when --first-parent option is given; in that case, the output represents the changes the merge brought into the then-current branch.