title: how to fix merge conflicts before merging
body: <p>When I try to merge a <code>feature</code> branch into <code>master</code>, I get a merge conflict every now and then.</p>
  
  <p>Now the obvious solution is to just manually resolve the conflict during the merge.</p>
  
  <p>However, with <em>pull-request</em> based workflows (github, gitlab,...), this is somehow sub-optimal, as it puts all the work on the person who is in charge of actually merging the branch, rather than the submitter.</p>
  
  <p>A somewhat useful solution is to merge <code>master</code> into <code>feature</code> before submitting a PR, fixing all the conflicts.
  however, I have the feeling that this complicates the git history needlessly.</p>
  
  <p>So I wonder, whether there's a (simple) way to prepare the <code>feature</code> branch so it can be merged cleanly into <code>master</code> (<em>after</em> the fact that the two branches have diverged significantly).
  Ideally the fixup can be done in multiple commits.</p>