title: Git individual file history lost with git subtree
body: <p>I'm merging 2 git repositores (old1 &amp; old2) into 1 (new1). My requirements are to merge all branches &amp; to keep the git commit history. First one I can achieve but I'm struggling with the commit history.</p>
  
  <p>This is the command I execute to merge the old1 repo in a sub folder of the new1: <code>git subtree add -P old1 https://github.com/example/old1.git master</code></p>
  
  <p>Output of <code>git log --graph --oneline --decorate --all</code>:</p>
  
  <pre><code>*   ad4fcb6 (HEAD -&gt; master, origin/master, origin/HEAD) Add 'komed-connector/' from commit '50b42475113c295c66c4050b3b0f119a6ebff62b'
  |\  
  | * 50b4247 Updated komed-shared
  | *   1a5435a Merge branch 'master' into openshift_build
  | |\  
  | | *   8aa90aa Merge branch 'r/3.4'
  | | |\  
  | | | * a6cea77 updated shared
  | | * | a40c782 Updated komed-shared
  ...
  </code></pre>
  
  <p>So far so good: git commit history is kept. But if I'm inspecting the git commits of a single file in the new sub folder it doesn't show all commits:
  <a href="https://i.stack.imgur.com/UAMEy.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UAMEy.png" alt="enter image description here"></a></p>
  
  <p><strong>How can I merge 2 repos into 1 and keep the individual file git commit history?</strong> So when running <code>gitk old1/Dockerfile</code> git shows me all commits that happened on the old repository.</p>