Fix agent forwarding inside a mosh session

fix_agent_forwarding_mosh.md

Mosh doesn't provide proper support for agent forwarding, generating error messages like this one:

Permission denied (publickey)

in response to a git clone.

For adressing the issue, follow bellow steps:

1. Open an separate SSH session with agent forwarding enabled in another terminal: ssh -A user@server
2. In your mosh session execute the given command for setting SSH_AUTH_SOCK to the last created ssh-agent socket:

export SSH_AUTH_SOCK=$( \
  find /tmp -path '*/ssh-*' -name 'agent*' -uid $(id -u) -printf "%T+\t%p\n" 2>/dev/null \
    | sort \
    | tail -n1 \
    | awk -F'\t' '{print $2 }' \
)

3. Run git clone ... or whatever you wanted.
4. When you are done, disconnect the SSH session