title: Select private key to use with Git
body: <p>I have 2 Git servers that require 2 different SSH keys.</p>
  <p><code>git clone user1@server1:blahblahblah</code> uses <code>~/.ssh/id_rsa</code>, but I need to specify which key to use depending on the server I am connecting to.</p>
  <p>What Git command-line parameter does this job? (I am running Linux.)</p>