I have a very early patch for backup development sources with --allsource option. The idea is to be able to backup all source code even when its svn/git/bzr/hg etc to .src.tar.gz files. This way we can have backup source in case the something goes down or if we mail dvd to place with spotty internet there will get full source code of all of archlinux. No need to download stuff when building. Like i said this is very early patch. I release it now cause i don't really do pacman coding. The source will be download to $startdir then tar.bz2 to $srcdir/$pkgname-$pkgver.tar.bz2. The source is still not added into the .src.tar.gz files yet. I think source array and md5sum array will have to be added for all of it to be all package up. I hope this helps.