title: Changesets candidates for merging showing up over and over again
body: <p>I have a main line called "Main" and a "Dev" line. Dev is child of Main.</p>
  
  <pre><code>Main
    ^
    |
  Dev
  </code></pre>
  
  <p>Actually, Main is used as a normal Dev branch, so both are checked-in new work continuously.</p>
  
  <p>From time to time, we decide to merge both. Pull Dev changesets to Main and the other way around. I guess we've not doing this correctly. We change files during merges, etc. In one situation we have created a branch from Dev to stabilize. Guess this was a mistake.</p>
  
  <p>The problem is, some changesets are "persistents", they keep showing up in merge window, also in "tf merge /candidate" command, as if they weren't merged already.</p>
  
  <p>I guess I could do a tf /discard and that would make the changeset disappear. Shouldn't it be this way?</p>
  
  <p>What is more, sometimes a merge reappers or even disappers after merging another changeset. Guess it is a somehow related changeset from another merge operation. In the course of getting rid of these, one single changeset is merged more than once.</p>
  
  <p>PS: Have tried tf /discard, tf /discard /baseless, tf /baseless handling conflicts. Nothing works. Did not try /force because I'm not keen on redoing all conflicts AFAIK.</p>