Diff-debs

[Jonathan Carter]

Hi Ubuntu devel list

I want to know how plausable this is.

I was thinking this morning about getting the download sizes smaller for
.deb files (there are probably entire teams of people working on this,
so this might just be a millionth monkey thing), and I've wondered why
there aren't a deb format that contains diff's between one release and
another, let me ellaborate.

On the deb server, you have deb-dif files, which would be files that
contain the diffs to the files in the package between one release of
Ubuntu and another. At the client side, you have a line in APT similar
that starts with deb-dif that points to the deb server, then a user
could just apt-get deb-dif-upgrade to download the differences between
the previous release and the current release. dpkg could even build a
package from existing files and the diff files so you would still end up
with the exact same .deb file in /var/cache/apt/packages. deb-dif could
use md5sums which is already there to check if a local file has changed,
and whether it needs to fetch that single file off a mirror containing
the file.

You could probably do it with unstable versions too, but it will
probably require lots of diskspace, unless you have some kind of
checkpoint system.

So, is there any big practical or other reason why this is not possible,
I haven't been able to think of one on my own so far.

-Jonathan