SSH host verification fails when IP changes (git succeeds) #2334
Description
Our git server is behind a load balancer, so the IP changes frequently. This is the git behaviour:
G1. On first clone, it says the authenticity of the host cannot be established, here's the fingerprint, do you want to trust it. If the user says yes, an entry is added to the ~/.ssh/known_hosts file in the form <hostname>,<ip> <key type> <fingerprint>.
G2. On the first clone after the IP changes, git sees an entry for the same host name with the same fingerprint and a different IP, adds an entry to the ~/.ssh/known_hosts file in the form <ip> <key type> <fingerprint>, and warns the user that this took place. This only happens when the host name and fingerprint are identical.
This is the Julia behaviour:
J1. On first clone, it shows "SSH host verification: the server <hostname> is not a known host. Please run ssh-keyscan <hostname> >> ~/.ssh/known_hosts in order to add the server to your known hosts file and then try again.".
J2. If the user does that, then entries in the form of <hostname> <key type> <fingerprint> are added to the ~/.ssh/known_hosts file are added.
J3. On the first clone after the IP changes, Julia succeeds
Mixing these can cause interesting behaviour.
J1, J2, G2 is fine, though notably git still adds those IP entries to the ~/.ssh/known_hosts file.
G1, J3 does not work. Instead Julia will fail and say "SSH host verification: the identity of the server <hostname> does not match its known hosts record.". This is the problem.
I say Julia should either a) allow the connection or b) give the prompt to run ssh-keyscan, which will cause J3 to succeed.