Problem

Syncing uploads fails on some machines with:

rsync: empty remote host

sync_uploads() pointed rsync at a target like ':/…/uploads/' — an empty host before the colon — with the real host baked into --rsh (ssh … 'user@host'). GNU rsync tolerates the empty host (it falls back to the host in the rsh command), so it works on Linux and Homebrew rsync. But openrsync — the /usr/bin/rsync Apple ships on macOS 15+, and the BSDs — validates the target and rejects an empty remote host outright, before it even runs the transport.

Two related fragilities in the same construction:

• the --rsh value was double shell-escaped — generate_ssh_command() returns an already-escaped command, then assoc_args_to_str() escaped it again. GNU rsync's -e parser peels the extra quotes back off; stricter parsers may not.
• it carried -t (request a TTY), inherited from generate_ssh_command()'s interactive-wp purpose, which is wrong for rsync's binary stream.

Fix

Build the rsync invocation directly instead of reusing generate_ssh_command():

• Alias::get_rsync_location() — a standard [user@]host:path location, so the host is always explicit (no empty-host target).
• Alias::get_rsync_rsh() — a transport-only ssh -T [-p port] [-i key], escaped exactly once; -T keeps rsync's stream off a TTY.

generate_ssh_command() is unchanged and still used by run_command() / export_db().

Before / after

- rsync … --rsh='ssh -t -q '\''user@host'\''' ':/…/uploads/' '/…/uploads/'
+ rsync … --rsh='ssh -T' 'user@host:/…/uploads/' '/…/uploads/'

Testing

• Reproduced end-to-end against a real sshd in Docker, including a hostile RequestTTY force ssh_config; the standard user@host:path form transfers and verifies by checksum.
• Matches a real openrsync failure (rsync: empty remote host) reported by a macOS user.

Follow-up

• Unit tests for get_rsync_rsh() / get_rsync_location(), plus a forced-TTY fix for export_db(), are in a follow-up branch.
• proxyjump is not carried into the transport (it was already unused for rsync — Alias::create() never captured it), so no regression; trivial to add if needed.