title: git proper way to fix topic after branch merge
body: <p>I'm new to Git and for now I'm only working with a local repository but I will eventually share my work with other developers. I'm trying to figure out what is the proper way of fixing code on a topic branch after it's been merged back to the master branch. Here's what I have:</p>
  
  <p><img src="https://i.stack.imgur.com/s9QU7.png" alt="enter image description here"></p>
  
  <p>My topic was implemented in C2 in a topic branch and then merged on the master branch. There's been another commit C5 on master for a different topic. Now I just found an issue in with the feature implemented in C2. Should I fix it in the topic branch as C6 then merge again on the master branch? Or should I just get rid of the topic branch since it's been already merged and just fix it directly in the master branch?</p>
  
  <p>Ideally I would like to keep the C2 and C6 in a single commit so that when we implement remote repository I can push a clean history. But I don't think I can just squash C2 and C6 because of the merge. Is there a way to do this?</p>
  
  <p><strong>What would be considered good practice to fix a topic after it's been merged?</strong></p>