title: Merge two Git repositories without breaking file history
body: <p>I need to merge two Git repositories into a brand new, third repository.  I've found many descriptions of how to do this using a subtree merge (for example <a href="https://stackoverflow.com/a/1426163">Jakub Narębski's answer</a> on <a href="https://stackoverflow.com/questions/1425892/how-do-you-merge-two-git-repositories">How do you merge two Git repositories?</a>) and following those instructions mostly works, except that when I commit the subtree merge all of the files from the old repositories are recorded as new added files.  I can see the commit history from the old repositories when I do <code>git log</code>, but if I do <code>git log &lt;file&gt;</code> it shows only one commit for that file - the subtree merge.  Judging from the comments on the above answer, I'm not alone in seeing this problem but I've found no published solutions for it.</p>
  
  <p>Is there any way do merge repositories and leave individual file history intact?</p>