How can I find a changelog of core utility versions in OS X? I often research what utilities are available on different POSIX-like operating systems in the interest of portability, but I haven't been able to find a stable listing of what versions of various utilities are included with different releases of OS X. I usually just keep the latest version of OS X on my own machine, so I can't simply read the manpages of older versions to see what features are available. Is there a listing or some other way to find out what UNIX features have changed between releases?
Apple documents the open source components for each release at the web page:


http://www.opensource.apple.com


Internally, they clearly do work before it's publicly documented as we have 10.9.2 out today but only 10.9 is listed publicly with the versions.