title: git merge a file with previous commit
body: <p>I am a git newbie, sorry if this is a absolute beginner question. Is there a way to merge a file with a previous commit.</p>
  
  <p>What I want to achieve with this is, I have a settings file which keep, well, settings. When I branched out, I changed for example db settings, in order to be able to try out things. Now I merged that branch with master. Now I don't want to checkout previous version of settings file because, I made some adjustments to it which is require by new feature. So I want to merge a file with previous commit.</p>