Could distributed tarballs be compressed with xz instead of bzip2?

[Ulrich Mueller]

It would be considerably smaller (sizes are for "bzip2 -9" and "xz -6"
which is the default):

   51056640 emacs-24.0.92.tar.gz
   41410560 emacs-24.0.92.tar.bz2
   34443264 emacs-24.0.92.tar.xz

Also xz can be uncompressed much faster:

   $ time bunzip2 emacs-24.0.92.tar.bz2
   real    0m11.840s
   user    0m10.393s
   sys     0m0.423s

   $ time unxz emacs-24.0.92.tar.xz
   real    0m4.251s
   user    0m3.833s
   sys     0m0.412s