Instead of using the hostname `%h`, which can be changed by the
~/.ssh/config file, use the commandline-given hostname `%n`.
This allows to alias a host with different hostnames, which then point
to different configurations. A common use-case for this is if you have
multiple accounts on github with each access to different private repos:
Host github.com
IdentitiesOnly yes
User git
IdentityFile ~/.ssh/id_rsa
Host customer.github.com
IdentitiesOnly yes
User git
IdentityFile ~/.ssh/customer
HostName github.com
Without this change, if a connection was established with the first
github.com alias, then the user would try to pull a repo from the second
account, ssh would re-use the SSH connection which doesn't have access
to that repository.
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