title: git pull request failed with “Permission denied (publickey)” error
body: <p>I have tried to pull my official repository to my local machine using</p>
  
  <pre><code>git pull git@github.com:x/x_project_management_app.git master
  </code></pre>
  
  <p>but it failed with error</p>
  
  <pre><code>    Permission denied (publickey).
  fatal: The remote end hung up unexpectedly
  </code></pre>
  
  <p>I have regenerated and added my system ssh-public key to my github account,I tried with different  system also,but I'm still facing same error. How can I fix it?</p>