How to extract Mac OS xip archive
xip is an old archive format used to distribute XCode. it's actually an xar format but with ability to be signed. If you installing the same software multiple times and don't want to spend time to verify known to be valid signature, instead of xip -x do the following (you can use xar -x -f instead of bsdtar xvf):
bsdtar xvf Archive.xip
ditto -x Content .