`ssh-add -D` sends `SSH_AGENTC_REMOVE_ALL_IDENTITIES` and then `SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES` (`SSH_AGENT_reserved9` in the code).
ssh-add -DsendsSSH_AGENTC_REMOVE_ALL_IDENTITIESand thenSSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES(SSH_AGENT_reserved9in the code).