[Unison-hackers] Unison and extended attributes (xattr) on Tiger?

[Trevor Jim]

One important detail not mentioned so far: cross-platform
support.  How do you sync a file with extended attributes
on Mac to Windows or Linux?  For forks, type, creator,
there is an existing standard way of doing this that we
have coopted.  I don't know whether that supports all the
attributes you want.  (We are using Apple Double files.)

Note that when Apple extended rsync etc. they did not deal
with the problem of cross-platform sync.  Others have had
to work on that.

Here is an article about metadata support for backup tools
on OS X, it has some useful information:

   http://blog.plasticsfuture.org/2006/03/05/the-state-of-backup-and- 
cloning-tools-under-mac-os-x/

Regarding the hooks into the OS functions to read attributes,
etc., there are two difficulties.  First, Apple has not necessarily
done a good job documenting this stuff, in my experience.
Second, these functions might exists in 10.4 but not in 10.3,
so, there are issues similar to what happens for cross-platform
support.

My experience adding support for resource forks, etc., is that
this is something that needs a lot of care.

-Trevor