title: resolve conflicts on git merge octopus
body: <p>Octopus merge means to merge more than 2 heads.</p>
  
  <p>How should the user to compare files using ordinal 3-way merge tools?</p>
  
  <p>3 files are passed to the merge tool: BASE, LOCAL, REMOTE</p>
  
  <p>How many and what combinations required for 3 heads?</p>