apt-offline should use patch-delta when downloading the index from server/servers

[rickysarraf]

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=795487

Package: apt-offline
Version: 1.6.1
Severity: wishlist

Dear Maintainer,
From couple of years back Debian has has been using the concept of
diff. when updating the index.

https://wiki.debian.org/RepositoryFormat#indices_difference_files_.28diffs.29

What it basically does is calculate the delta between the index
Packages.gz or whatever it is and the one installed on the system and
only in case of hash sum mismatches or something it downloads a clean
copy from upstream/debian.org otherwise calculates diffs which make it
a much cheaper operation.

Now apt-offline aims to help in the same regard and the issue hurts
most of people who are in developing countries where we do not have
access to fat pipes and in some cases we have to even pay for a single
bit. In such scenarios if apt-offline is able to use the diff process,
it would be cheaper and faster operation as well.

Look forward to seeing it in a newer version of apt-offline. From what
I could figure out, apt does have some support of it.

Look forward to hopefully see the idea implemented in a new release.

-- System Information:
Debian Release: stretch/sid
APT prefers unstable
APT policy: (500, 'unstable'), (500, 'testing'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 4.1.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_IN, LC_CTYPE=en_IN (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages apt-offline depends on:
ii apt 1.0.10.1
ii less 458-3
ii libpython2.7-stdlib [python-argparse] 2.7.10-3
ii python 2.7.9-1
pn python:any

Versions of packages apt-offline recommends:
ii debian-archive-keyring 2014.3
ii python-magic 1:5.22+15-2
ii python-soappy 0.12.22-1

apt-offline suggests no packages.

-- no debconf information