It should be possible to use the value of
pathconf("path/to/destination", _POSIX_TIMESTAMP_RESOLUTION) to
determine the minimum timestamp resolution and to set
--modify-window accordingly by default.

http://www.opengroup.org/onlinepubs/9699919799/functions/fpathconf.html

Unfortunately, this does not seem to exist in Debian. :(

Maybe in the mean time, rsync chould use statfs(3)'s f_fsid field
and set --modify-window to a default of 2 for FAT/VFAT destinations?
I realise this is a hack, but it'd be useful until
_POSIX_TIMESTAMP_RESOLUTION became available.

Thanks,

The biggest problem with both solutions is that you would have to check
the filesystem / _POSIX_TIMESTAMP_RESOLUTION thing for every directory
you traverse, as there may be FAT filesystems on subdirectories or bind
mounts etc.; this may cause a hefty overhead.


Paul