title: SSH Connectivity to Heroku account fails
body: <p>Trying to configure Herokugit, accepted the default key (id_rsa) as the public key, changed the permissions to 600 as it complained its not secure. Now when i try to validate the ssh connection I get invalid file format error.</p>
  
  <pre><code>[coderhub@Coderhub-mac heroku]$ssh -v git@heroku.com
  OpenSSH_7.9p1, LibreSSL 2.7.3
  debug1: Reading configuration data /Users/coderhub/.ssh/config
  debug1: /Users/coderhub/.ssh/config line 1: Applying options for heroku.com
  debug1: Reading configuration data /etc/ssh/ssh_config
  debug1: /etc/ssh/ssh_config line 48: Applying options for *
  debug1: Connecting to heroku.com port 22.
  debug1: Connection established.
  debug1: identity file /Users/coderhub/.ssh/id_rsa.pub type 0
  debug1: identity file /Users/coderhub/.ssh/id_rsa.pub-cert type -1
  debug1: Local version string SSH-2.0-OpenSSH_7.9
  debug1: Remote protocol version 2.0, remote software version endosome
  debug1: no match: endosome
  debug1: Authenticating to heroku.com:22 as 'git'
  debug1: SSH2_MSG_KEXINIT sent
  debug1: SSH2_MSG_KEXINIT received
  debug1: kex: algorithm: curve25519-sha256@libssh.org
  debug1: kex: host key algorithm: ssh-rsa
  debug1: kex: server-&gt;client cipher: chacha20-poly1305@openssh.com MAC: &lt;implicit&gt; compression: none
  debug1: kex: client-&gt;server cipher: chacha20-poly1305@openssh.com MAC: &lt;implicit&gt; compression: none
  debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
  debug1: Server host key: ssh-rsa SHA256:8tF0wX2WquK45aGKs/Bh1dKmBXH08vxUe0VCJJWOA/o
  debug1: Host 'heroku.com' is known and matches the RSA host key.
  debug1: Found key in /Users/coderhub/.ssh/known_hosts:33
  debug1: rekey after 134217728 blocks
  debug1: SSH2_MSG_NEWKEYS sent
  debug1: expecting SSH2_MSG_NEWKEYS
  debug1: SSH2_MSG_NEWKEYS received
  debug1: rekey after 134217728 blocks
  debug1: Will attempt key: /Users/coderhub/.ssh/id_rsa.pub RSA SHA256:suGiIhQN6QphoPJwM4YecZDiTRjNZIPHh46ur58TbvA explicit
  debug1: SSH2_MSG_SERVICE_ACCEPT received
  debug1: Authentications that can continue: publickey
  debug1: Next authentication method: publickey
  debug1: Offering public key: /Users/coderhub/.ssh/id_rsa.pub RSA SHA256:suGiIhQN6QphoPJwM4YecZDiTRjNZIPHh46ur58TbvA explicit
  debug1: Server accepts key: /Users/coderhub/.ssh/id_rsa.pub RSA SHA256:suGiIhQN6QphoPJwM4YecZDiTRjNZIPHh46ur58TbvA explicit
  **Load key "/Users/coderhub/.ssh/id_rsa.pub": invalid format**
  debug1: No more authentication methods to try.
  git@heroku.com: Permission denied (publickey).
  </code></pre>