title: What happens if I merge a commit that has removed code my new feature depends on
body: <p>Say Alice and I have cloned a repository and been making changes. Alice commits her changes and pushes to remote. I then fetch that change and merge it with mine. Imagine Alice, in her latest commit, has removed a class called Vehicle. I in my turn, I have added a new class called Car that extends the Vehicle class. Now, when I merge her commit into mine, there's obviously going to be a problem. 
   Does this mean  that I have to examine the code and test it before merging? (Probably yes). What is the common practice in this situation?</p>