The additional-mirror setup already resolves user/hostname through ssh -G
so a ~/.ssh/config alias works, but never extracted port — Kopia's sftp
storage backend doesn't read ~/.ssh/config at all and defaults to 22
regardless of what the alias actually configures. Confirmed live: this
produced "server unexpectedly closed connection: unexpected EOF" on the
dry-run verification — Kopia connecting to the right host on the wrong
port, not a credentials or host-key issue, which is exactly why plain
`ssh main` kept working the entire time this was being debugged (it reads
the alias's Port line correctly).
Now parses `port` out of the same ssh -G output, defaults to 22 if absent
(matching ssh's own default), and passes --port= through to both the
dry-run check and the persisted EXTRA_MIRROR_ARGS string — the latter
matters as much as the former, since that's what every actual scheduled
sync reuses afterward, not just the one-time verification.
Verified the parsing against three cases: a custom-port alias, a
default-port alias, and an unresolvable alias — all three resolve to the
correct port with no manual intervention needed.
Claude
1bb7498567