title: Github: Use ssh key to use in only one repository or organization
body: <p>It is possible to create an SSH Key who only have access to one repository or one organization and all the other ones will be rejected?</p>
  
  <p>For example, you have access to this 4 repositories:</p>
  
  <pre><code>git@github.com:MyUser/repo-u1.git
  git@github.com:MyUser/repo-u2.git
  git@github.com:OrgRepo/repo-o1.git
  git@github.com:OrgRepo/repo-o2.git
  </code></pre>
  
  <p><strong>First case:</strong></p>
  
  <p>You create an ssh-key who only have access to <code>OrgRepo</code>. So, if the key is stolen and hacked the hacker only can have access to <code>OrgRepo/repo-o1.git</code> and <code>OrgRepo/repo-o2.git</code> but if he tries to clone the <code>MyUser/repo-u1.git</code> or <code>MyUser/repo-u1.git</code> will be rejected.</p>
  
  <p><strong>Second case:</strong></p>
  
  <p>You create an ssh-key who only have access to <code>MyUser/repo-u2.git</code>. So, if the key is stolen and hacked the hacker only can have access <code>MyUser/repo-u2.git</code> but will be rejected for the other 3 repositories.</p>