## Package build instructions

Get the various orig tarballs and unpack it:

    origtargz --unpack

Build the package with your favorite build tool, eg:

    # pbuilder + debuild
    pdebuild
    # sbuild
    sbuild

Build the package in a docker container:

    # Build a docker image that contains the build dependencies,
    # according to the file debian/control.
    ./debian/helpers/docker.sh build
    # Build the package as normal user
    ./debian/helpers/docker.sh run-user dpkg-buildpackage -us -uc
    # Build the package as root (to run more tests)
    ./debian/helpers/docker.sh run-root dpkg-buildpackage -us -uc

Build a source package on your machine:

    dpkg-buildpackage -dS

Cleanup:

    # Remove all non-debian files
    origtargz --clean
    # Remove all non-versioned files and hard-reset
    git clean -dfx && git reset --hard


## Package update instructions

Update the version in 'debian/changelog':

    V=20.10.0
    dch --newversion ${V:?}+dfsg1-1 "New upstream release [${V:?}]"

Add git commits corresponding to the new version in the files:

    vi -O debian/helpers/{cli,engine}-gitcommits

Run uscan as such:

    uscan -v -dd --download-current-version 2>&1 | tee uscan-logs

Show which Files-Excluded patterns appear to be useless:

    ./debian/helpers/uscan-summary.sh < uscan-logs

Remove those from Files-Excluded and Build-Depends.

    vi -O debian/{control,copyright}

Unpack the orig tarballs:

     origtargz --unpack

Check the global vendor tree:

    ./debian/helpers/ls-vendor.sh

Add unwanted items in Files-Excluded:

    vi debian/copyright

Cleanup, run uscan again. Then fix the build.
     

## Multiple Upstream Tarballs (MUT)

Overview:

- `d/watch`: ask uscan to invoke the script `debian/get-orig-source.sh`.
- `d/get-orig-source.sh`: this is where are listed all the orig tarballs that
  need to be downloaded, and where the job is done (download and repack).
- `d/rules`: the various components are explicitly handled here.

In `d/rules`, you will find that there are two ways to build components:

- `DH_GOPKG=component dh_auto_build` leads to a standard, full build of
  the component. It builds all the package directories found (think `go
  list component/...`)
- `DH_GOLANG_BUILDPKG=component dh_auto_build` only builds the main package.

A full build (using `DH_GOPKG=...`) is definitely needed for components that
produce a binary (ie. libnetwork). But for components that are only used as
build dependencies of docker, a full build is not mandatory,
we can simply run `DH_GOLANG_BUILDPKG=...`. It will at least attempt to build
the main package.

Attempting to build every component fully with `DH_GOPKG=...` is actually time
consuming, and in the end not very productive. For build-deps, only some parts
of the code are used by docker during the build, so there's no need to spend
time fixing FTBFS in parts of the code that are not used anyway.



## "stable" versus "edge" releases

As per [1], starting with Docker 18.09, CE "stable" releases will be
supported for 7 months. See [2] for details.

This package should only ever ship "stable" Community Edition (CE)
releases.

Docker version numbers are derived from date, e.g. `date +%g.%m`.

The every-month releases are "edge" (17.04, 17.05, etc), are only supported
for the duration of their release month. Stable releases have longer
support cycles. Monthly "Edge" releases should be avoided.

[1]: https://docs.docker.com/install/
[2]: https://docs.docker.com/release-notes/docker-ce/


## Incompetent upstream release process

Upstream is notorious for incredibly sloppy versioning. Docker components
are inconsistently versioned; don't depend on same version of common
libraries and different revisions of dependency libraries are privately
vendored. Basically upstream couldn't care less about consistent, semantic
versioning and re-usable components. Shameful abomination of good software
development practices... :(

**An overview of the various docker repositories**

Some repositories used to release on a regular basis, then stopped:

  * https://github.com/moby/moby          : last release on Jun 28, 2017
  * https://github.com/docker/distribution: last release on Jul 21, 2017
  * https://github.com/docker/libnetwork  : last release on May 8, 2016

This seem to be due to the split between Moby and Docker, although it is highly
undocumented. For the Moby repository, you have to dig up this kind of thread:
"https://github.com/moby/moby/issues/33951#issuecomment-312995683"

Some repositories never really had any releases:

  * https://github.com/docker/cli
  * https://github.com/docker/go-events
  * https://github.com/docker/swarmkit

**The docker-ce super repository**

docker-ce is the super repository from where Docker Community Edition is
produced, and this is where things get messy.

Basically this is where the code from the docker engine (github.com/moby/moby)
docker client (github.com/docker/cli) is pulled together. But how? Looking at
the git history, we can see cherry-picked commits, merge requests, standalone
commits, and probably other things... In the end, when a docker-ce version is
released, it doesn't seem to correspond to a particular commit of moby/moby or
docker/cli.

At some point I thought we should ignore docker-ce, and instead package
moby/moby and docker/cli separately. But because of the workflow described
above, I now think it's a very bad idea. We have no idea of which version of
moby/moby and docker/cli work together (no semantic versions), and we can't
really find this information from a tag in docker-ce.

So we'd better package docker-ce instead.

See https://github.com/moby/moby/issues/38063#issuecomment-431324613
for details.


**Docker-ce releases**

Upstream tags releases in "github.com/docker/docker-ce" and we have to ship
matching bundle of Docker engine, and Docker CLI from that repository.

Docker-ce releases monthly, with a 2 or 3 release candidates before the
final release. Other than quarterly "stable" releases there doesn't seem to
be any long-term releases. The fact that there are release candidates
probably indicates that bugs are reported, test suites are run, and things
are fixed between various rc (hopefully).

On top of that Docker depends on very particular commits of

  * github.com/containerd/containerd
  * github.com/docker/libnetwork
  * github.com/docker/swarmkit

None of the above repositories have relevant tags.

**Docker code base is spread among several name spaces.**

We've made a mistake trying to treat it as several reusable components.

Upstream abuse of versioning practices is a shameful and incompetent
disgrace. Docker people, if you are reading this I hope you feel sorry.
I, Dmitry Smirnov <onlyjob@debian.org>, find it difficult to politely
express how much I despise your release process.


## Circular dependencies

Let me explain practical problem with dependencies. Docker and Libnetwork
both depend on each other and on "sirupsen/logrus". When in the 2018 the
latter exhibited minor/trivial problem I could not upload neither Docker
nor Libnetwork because each FTBFS in the "other" dependency. That's why
starting with 17.12.1 libnetwork has been incorporated into "docker.io".


## Docker package vendoring policy

As highlighted above, it is unsustainable and impractical to package
individual Docker "components". Many libraries of Docker name space are
only ever used by Docker and depend on "github.com/docker/docker" which
makes them part of Docker code base.

Combined with upstream resistance to good versioning practices, we have to
ship Docker bundle producing (only) reusable package from multi upstream
tarball (MUT) source package.

Some vendored microlibraries, unless semantically versioned, are not
worth to be introduced as standalone source package.

Therefore "docker.io" source package will ship all essential Docker
dependencies to avoid circular dependencies. Main criteria for inclusion of
a dependency library into "docker.io" source package is dependency on
"github.com/docker/docker". Additional criteria is assessment whether
Docker dependency is reusable (e.g. semantically versioned and used by
other packages). Age of tags is to be considered as Docker team stopped
tagging most of their dependencies in favour of vendoring them by some
random commit.


## Bundled versus external libraries

### runc

We should make an effort to use "runc" package which no longer depends on
Docker since 1.0.0~rc5 (no circular/mutual dependency). runc upstream is
tagging releases so it satisfies non-bundling criteria mentioned above.

In 2017 all reverse build-deps of runc-dev were broken when Balint Reczey
<rbalint@ubuntu.com> forked "runc" source package as "docker-runc"
versioned to match Docker expectations.
New package "golang-github-opencontainers-docker-runc-dev" had explicit
Conflits with "golang-github-opencontainers-runc-dev" effectively hijacking
runc because all packages depending on runc-dev also depend on docker-dev
(which depends on docker-runc-dev) hence runc-dev could not be installed
together with docker-runc-dev. Maintainer of reverse runc-dev build-deps
was very unhappy...

Let me stress it again: Docker should not hijack runc's name space
"github.com/opencontainers/runc". Docker's fork of the latter have its
own name space: "github.com/docker/runc".

In the unfortunate situation if we ever have to use bundled runc in Docker,
we should NOT provide docker-runc-dev package ever again (or at least avoid
Conflicts with runc-dev at all costs). I suggest testing runc package for
run-time compatibility with Docker. That works well with Docker 17.12.1.

Do not be mislead by particular (random) RUNC_COMMIT that Docker expects
(e.g. `docker info`, "engine/vendor.conf") - we can/should not comply with
upstream's systematic abuse of versioning.

Perhaps expected commits are not to be trusted at all: for instance in
17.12.1, CONTAINERD_COMMIT in "engine/hack/dockerfile/binaries-commits"
does not match any of containerd commits in "engine/vendor.conf".


## Notable upstream bugs

 https://github.com/moby/moby/issues/37272
 https://github.com/docker/distribution/issues/2623
 https://github.com/docker/distribution/issues/2609
 https://github.com/moby/moby/issues/37930
