file syncing / folder watching over scp (not ftp)

Just some technical notes to my future self...

I wanted a file syncer, so that I could edit some webstuff locally on my Mac and see it immediately on refresh of the website I'm working on.

(I have a kind of clunky but useful textarea based online editor for my websites based on markitup, but since it submits as an old fashioned form POST rather than something clever with AJAX, I'm always losing my place, plus I haven't researched how to give it more of the IDE-ish features like line numbering, autotabbing and parens balancing)

I wasn't having much luck with Yummy's "FTP Watcher", as far as I could tell it can only be set to poll as low as one second, which is a bit too slow. (My gold standard right now is IntelliJ - its cleverness is to notice that it has lost focus, and THEN run the file copy. This works much better and transparently than I would have expected for stuff that doesn't have a build cycle.)

The best bet I found was sshync -

(In turn I had to follow its instructions to install and run ssh-copy-id - but then it was asking me for my passphrase not remote password each time.  So I found some instructions on running ssh-add and now it does what I wanted.

The only other note is I misguessed how to specify the source and destination folders, I had thought it would be like
sshync ~/dev/website-folder/ username@server:/site-parent-folder/website-folder/
but instead it was
sshync ~/dev/website-folder/ username@server:/site-parent-folder/
i.e. the destination is kind of like the parent instead of the peer. And I wanted to avoid worrying about wildcards.

FOLLOWUP:
to be more specific, after using this setup on one system for a while, and then doing it on a different system...

I had to get and run ssh-copy-id, using
brew install ssh-copy-idand follow the instructions at https://www.ssh.com/ssh/copy-id - I already had by key generated, so I used ssh-copy-id on the public key in the folder.

Then my notes say I tend to have to run
exec ssh-agent bash
ssh-add
each time before starting sshync , otherwise it keeps asking me for my password