title: Git - how to force merge conflict and manual merge on selected file
body: <p>We maintain web application which has common master branch and many parallel branches, one for each installation, each have few specific changes. Source code is managed in git and it is terrific tool when we need transfer features and bugfixes from master branch into parallel ones. But are few files that are sensitive and automatic merging usually give bad results. So merging would be much easier if they can be somehow marked and every merge would result in conflict requiring manual merge.</p>
  
  <p>I searched for an answer :</p>
  
  <ol>
  <li>I am using <strong>--no-commit</strong> and <strong>--no-ff</strong> merge options, but it is not the same.</li>
  <li><a href="http://kerneltrap.org/mailarchive/git/2008/11/9/4047284/thread" rel="noreferrer">Here</a> and <a href="http://git.661346.n2.nabble.com/force-a-merge-conflict-td1477477.html" rel="noreferrer">here</a> someone asks the same question but with no solution.</li>
  <li>Similar case seems to be <a href="https://stackoverflow.com/questions/4515679/git-workflow-can-i-prevent-a-certain-file-from-being-merged-to-another-branch-bu">how to prevent file being merged</a> using .gitattributes containing: <strong>somefile.php merge=ours</strong> . I tried to find some merge option which would generate conflict or force manual merge but found none so far.</li>
  <li>.gitattributes containing: <strong>somefile.php -merge</strong> is never merged automatically and therefore forcing manual merge. It is 90% solution, but what I seek is to try automatic merge and mark it as conflict regardless it is successful or not. <strong>But this is so far closest to solution.</strong> <em>(...thanks Charles Bailey for clarification...)</em></li>
  <li>Someone suggest to write custom merge driver (<a href="https://stackoverflow.com/questions/3038185/manual-merge-on-git">1</a>, <a href="https://stackoverflow.com/questions/928646/how-do-i-tell-git-to-always-select-my-">2</a>), but how to do it is far from clear to me. </li>
  </ol>
  
  <p><strong>edit:</strong> variant 4. description</p>