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new experimental debdelta feature --format=unzipped

Dear all,
I just uploaded into experimental a new version 0.42exp of debdelta (
you may find some binaries also in [3] ).

This version adds an experimental feature : if you call
'debdelta-upgrade' with the option '--format=unzipped' , then in the
recreated deb the data.tar part will not be compressed.  This may speed
up the 'debdelta-upgrade' + 'apt-get upgrade' process. Indeed, writing
to hard disk is fast (let's say 5MB/sec, but usually much more); whereas
compressing random data with 'bzip2 -9' or 'lzma -9' is much slower
(let's say 2.0MB/sec and 1.5 MB/sec) ; and moreover the compressed data
is then decompressed by dpkg when installing; so avoiding the
compress/decompress should be a win/win (unless you run out of disk

Please test it and tell me what you think.
(Let me mention that old deltas in the server do not support this new
feature, so you may get some warnings for some days). (I also want to
thank Guillem Jover for proposing this idea, in a mail in

(In the future, we may add an even more aggressive behavior, whereby the
data is directly piped from debdelta thru dpkg to the hard disk ; this
would be in the spirit of [2] ; I already adapted the deltas to support
this, but it needs  changes in APT and in dpkg , it may be done as  part
of [4] ).


[1] http://debdelta.debian.net
[2] http://wiki.debian.org/SummerOfCode2010/StreamingPackageInstall
[3] http://debdelta.debian.net/squeeze-backports/
[4] http://wiki.debian.org/SummerOfCode2011/AptDebdeltaIntegration

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