ssh: Tokens and parameter expansion

ssh provides a number of tokens that will be dynamically replaced in various connection options e.g.:

• %n - the remote hostname (as provided on the command line)
• %h - the remote hostname

See more in the man pages: man ssh_config | less '+/^TOKENS'

It also supports referencing local environment variables via ${...} syntax, and since that supports bash expansion there are possibilities for sneaky hacks like: https://blog.jbowen.dev/tips/ssh-tmux/