title: The argument "-i" passed to GIT_SSH_COMMAND is being ignored
body: <p>I want to use other IdentityFile for git. I want to use it dynamically, not via config. I'm doing this:</p>
  
  <pre><code>  $ GIT_SSH_COMMAND='ssh -i /home/my_user/.ssh/id_ed25519' git pull origin master
    repository access denied.
    fatal: Could not read from remote repository.
  
    Please make sure you have the correct access rights
    and the repository exists.
  </code></pre>
  
  <p><strong>The pub key "id_ed25519.pub" is at my bitbucket.</strong></p>
  
  <p>And this fails too:</p>
  
  <pre><code>  $ git pull origin master
    repository access denied.
    fatal: Could not read from remote repository.
  
    Please make sure you have the correct access rights
    and the repository exists.
  </code></pre>
  
  <p>And:</p>
  
  <pre><code>$ git remote -v
  origin  git@bitbucket.org:company123/repo456.git (fetch)
  origin  git@bitbucket.org:company123/repo456.git (push)
  </code></pre>
  
  <p><strong>Adding</strong> <strong>"-v"</strong> to <strong>'ssh -i /home/my_user/.ssh/id_ed25519'</strong> reveals that my RSA key is being used, instead of ED. Why?</p>