copying differences to different directory

[Matt McCutchen]

On Tue, 2010-03-02 at 08:47 -0800, js_spamfree-rsync at yahoo.com wrote:
> sorry for the confusing subject line. i couldn't think of a better way
> to say it. 
> 
> i'm wondering if rsync can perform the following action:
> 
> Compare contents of Directory A (master) to Directory B and copy any
> differences from Directory A to Directory C (example below)

You want --compare-dest.

Note that --compare-dest is based on the quick check, which uses size
and mtime by default.  If you have files in A that are identical to the
ones in B except for mtime and you want to omit such files from C,
you'll need to use --checksum /and/ make sure not to preserve mtimes.

-- 
Matt