title: git mergetool reports "No files need merging"
body: <p>For some reason lately, every time I pull and get a merge conflict, running <code>git mergetool</code> reports "No files need merging":</p>
  
  <pre><code>$ git pull
  First, rewinding head to replay your work on top of it...
  Applying: replaced home button with Cancel
  Using index info to reconstruct a base tree...
  Falling back to patching base and 3-way merge...
  error: Your local changes to the following files would be overwritten by merge:
      Classes/Controllers/HomeController.m
  Please, commit your changes or stash them before you can merge.
  Aborting
  Failed to merge in the changes.
  Patch failed at 0002 moved rollback into cancel button in log watching
  
  When you have resolved this problem run "git rebase --continue".
  If you would prefer to skip this patch, instead run "git rebase --skip".
  To check out the original branch and stop rebasing run "git rebase --abort".
  
  $ git mergetool
  No files need merging
  </code></pre>
  
  <p>If I run <code>git rebase --abort</code> and pull again, either the same thing happens on a different conflict, or the pull succeeds with no merge conflict. There are no remote changes between these pulls, so it's not as though the conflict went away.</p>
  
  <p>Here's how this branch and the remote are configured:</p>
  
  <pre><code>[branch "develop"]
          remote = origin
          merge = refs/heads/develop
          rebase = true
  [remote "origin"]
          url = &lt;my repo url&gt;
          fetch = +refs/heads/*:refs/remotes/origin/*
  </code></pre>