Add modern Debian/Ubuntu packaging for Python 3 (PEP 517, autopkgtest)

[sarsolot]

Add modern Debian/Ubuntu packaging for Python 3 (PEP 517, autopkgtest)

Summary

This PR adds/upgrades in-tree Debian/Ubuntu packaging for the Python 3 version of cfv (the python3 branch).
The existing debian/ directory in the repo appears to be from the legacy Python 2 era; this replaces it with modern packaging suitable for current Debian/Ubuntu workflows.

What’s included

• Modern debhelper-compat (= 13) + dh-sequence-python3
• PEP 517 / pyproject.toml build via pybuild (PYBUILD_SYSTEM=pyproject)
• Minimal debian/rules and Rules-Requires-Root: no
• autopkgtest:
  • cfv --help smoke test
  • Small functional test: generate a checksum file (sha1) and verify it (no network, no source-tree dependency)
• Installs the existing cfv.1 man page via debian/cfv.manpages
• DEP-5 debian/copyright (includes MIT BitTorrent code licensing)
• debian/watch included for future release monitoring
• Builds/tests are network-free

Tested

Locally verified on Ubuntu with:

• dpkg-buildpackage -b
• lintian -IE --pedantic (only remaining notes relate to upstream LICENSE placement, which is acceptable)
• autopkgtest -B . -- null (PASS)

Ubuntu PPA

For convenience (and to demonstrate it builds/installs cleanly), builds are published in Launchpad PPA:

• ppa:sarsolot/cfv

Notes for Debian

I’m not a Debian maintainer, but I tried to keep the packaging aligned with Debian best practices so it can be adopted with minimal changes later (mainly versioning/changelog targeting unstable / UNRELEASED and any maintainer-field conventions a sponsor may prefer).

Happy to iterate on this based on maintainer or sponsor feedback.

[lxp]

Thanks for your effort in updating the Debian packaging!

Since I do not know much myself about Debian packaging standards, I would suggest to just merge your changes, since it can only get better from the current broken state. I only noticed two things:

You do not run the unit and integration tests in the autopkgtests. Was this an intentional decision?
For example, the CI shows how to run them:

cfv/.github/workflows/ci-python3.yml

Lines 60 to 73 in 8533a22

	- name: Run unit tests
	run: python -W error -bb test/test.py --unit --exit-early
	- name: Run integration tests (internal)
	run: |
	ulimit -n
	ulimit -n 4096
	python -W error -bb test/test.py -i --exit-early
	- name: Run integration tests (external process)
	run: |
	ulimit -n
	ulimit -n 4096
	test/test.py -e --exit-early

Your current version 3.2.0+git20251102.8533a22-1~ubuntu25.10.1~ppa1 does not reflect the version the currently unreleased development version used by cfv:

cfv/lib/cfv/common.py

Line 29 in 8533a22

__version__ = '3.2.1.dev0'

Does the .dev0 suffix make problems in Debian package versioning?
(In Python packaging 3.2.1.dev0 is smaller than 3.2.1: https://packaging.python.org/en/latest/discussions/versioning/)

[sarsolot]

Thanks a lot for the review - much appreciated.

Even though I have been a long-time Debian/Ubuntu user (and admin), Debian packaging itself is something I am still actively learning, so the feedback was very helpful.

For now I:

• added the upstream unit + integration tests to autopkgtest (reusing the same commands as CI),
• aligned the snapshot versioning with upstream (3.2.1~dev0, so it upgrades cleanly to a future 3.2.1).

One thought: it might make sense to merge the packaging first for Ubuntu (PPA), but keep this Debian issue open. A working PPA and in-tree debian/ files are a good step, but they are not the same as an official Debian package yet.

Additionally, it may be smoother to finalize/merge the Debian packaging once the BLAKE3 and xxh/xxhsfv PRs are merged, so the packaging can reflect them properly (e.g. via Suggests: python3-blake3, python3-xxhash) rather than revisiting it again shortly after.

[lxp]

Thanks for the iteration, it looks good to me.

I agree that this PR does not fully solve #4, but it is the first milestone for solving the issue.

I have no objection to delay this PR until the others are merged. I will take a look at the BLAKE3 MR in the next days.