title: Is there a 'git sed' or equivalent?
body: <p>Let's say I want to rename a method in source code contained in a git repository. I could do this by hand, but the method name might be in multiple places (e.g., unit test, documentation, actual method). To check where the method is used, I use 'git grep'. I get 'git grep' to show only lines that I want to change, and then I don't have a workflow to automatically change those lines. </p>
  
  <p>I'm looking for an automated way (hopefully using git tools) to do this last step. I was hoping there was some sort of 'git sed' or equivalent, but I can't find any. </p>
  
  <p>The interface I'm thinking would be nice: git sed 's/old-method-name/new-method-name/g'</p>