Binary diffs for deb files

[john]

This has been discussed in ubuntu-devel before. Perhaps we should move
this discussion to
 https://wiki.ubuntu.com/APTPackageDeltas/talk
, as I understand that the core devs want to keep duplicated threads on
ubuntu-devel to a minimum.

On Tue, May 02, 2006 at 10:14:50PM +0100, James Hall wrote:
> Some other issues I have with zsync are:
> 
> 1. How easy would it be to recompress all the packages with the gzip
> --rsync flag?

This is not necessary with zsync, see:
http://zsync.moria.org.uk/paper/
(but this has been discussed before at length, and is also mentioned in
the talk page above)

> 2. How do we resign all these packages?

I believe the consensus was that it would be best to maintain binary
equality.

<snip>

> I will carry on testing compression methods and will fully evaluate
> zsync before dismissing it completely, although my initial feeling is it
> will do very little. 

My results suggested that zsync would reduce bandwidth to ~33% for
regular upgrades (not necessarily dist-upgrades) compared to 10%-5% for bsdiff.

> Currently there is no easy way I know of to make the repackaged ar files
> have the same checksum as the original, even tho the contents are
> identical.

My rather hackish plan was to just have another patch between `cat
control.tar.gz data.tar.gz` and the ar file. Since the amount of data in
the ar file that isn't part of the data.tar.gz or control.tar.gz is only
~100 bytes, including this patch in the debdiff shouldn't bulk up the debdiff
that much.

-- 
John C. McCabe-Dansted
Masters Student