CHANGES (u.c969c9ad6c5a7b32e79d0d626ab2deb5.dockerfile-opam.5.0.0.doc.CHANGES)

Major API iteration to:

switch to multistage container builds for smaller containers
instead of separate ocaml and opam containers, just generate a single opam one which can optionally have the system compiler or a locally compiled one.
explicitly support aliases for distributions, and allow older distributions to be marked as deprecated.

Other changes:

Mark OCaml 4.05.0 as a released stable version.
Remove the Alpine 3.5 camlp4 hack as it has been fixed in a point release upstream.
Add minimum constraint on sexplib in build rules (#6 reported by @smondet)
Add support for Alpine 3.6 and Debian 10 (Buster).
Bump the most recent Debian Stable to Debian 9.
Bump the most recent Alpine to Alpine 3.6.
Add OCaml 4.04.2 as the most recent compiler

There are also backwards incompatible changes to the package layout:

Split up OPAM packages into dockerfile and dockerfile-opam. The latter contains the OPAM- and Linux-specific modules, with the core DSL in dockerfile.
Port to jbuilder.

Add OCaml 4.04.1 to the stable released set.
Add Ubuntu 17.04 and Fedora 25 to the distribution list.
Setup OPAM2 wrappers in containers. This will enforce Linux namespaces upon building and installing the packages, preventing them from doing network access when they shouldn't or writing files where they shouldn't (#1 from @AltGr). These are not activated by default and are present in /etc/opamrc.userns in the relevant OPAM2 containers.

Remove support for ARM variants from the default distribution list. They will come back as explicitly supported multiarch targets, instead of the current qemu builds that are mixed up with x86_64 targets.
Always install OPAM from source on Alpine until upstreaming is complete.
Register 4.04 as a mainline compiler as well (fixes OPAM2).
Add support for Alpine 3.5 and OpenSUSE 42.2, and promote the Alpine:latest images to Alpine 3.5.
Do not install camlp4 by default in distributions.
Refresh aspcud remote proxy with url-escaping fixes (via @OCamlPro-Henry in ocaml/opam#2809)
Add Ubuntu 16.10 to the built-distros list.

Update for OCaml 4.04 release. Now the "latest version" of the compiler is 4.03.0 since many packages do not yet compile for 4.04.
Do not install camlp4 in the base OPAM switch by default, as the dependencies in upstream OPAM work well enough to pull it in on-demand.

Move Dockerfile.Linux to a separate Dockerfile_linux module, in preparation for Dockerfile_windows soon.
Avoid using ppx annotations for sexp in the interface files, since this breaks ocamldoc.
Add Dockerfile.pp for Format-style output.

Multiarch: Add Alpine 3.4 and Alpine/ARMHF 3.4 and deprecate Raspbian 7.
Add OpenSUSE/Zypper support and add OpenSUSE 42.1 to the default distro build list.
Add Ubuntu 16.10 to the distro list, and remove Ubuntu 15.10 from default build list now that 16.10 LTS is available.
Add Fedora 24 and make it the alias for Fedora stable. Also install redhat-rpm-config which is needed for pthreads.
Add an extra arg the Dockerfile_distro matrix targets to add more distros to the mix, such as Raspbian.
Support multiple OPAM versions in the matrix generation, to make testing OPAM master easier.
Always do an rpm --rebuilddb before a Yum invocation to deal with possible OverlayFS brokenness.
Support opam_version to distro calls to build and install the latest version of OPAM2-dev.
Add xz into Alpine containers so that untar of those works.
Expose the development versions of OCaml compilers.

Add released OCaml 4.03.0 into the compiler list, and break up the exposed variables into a more manageable set of stable_ocaml_versions and all_ocaml_versions.
Install centos-release-xen remote into CentOS6/7 by default so that depexts for xen-devel work.

Dockerfile_distro.generate_dockerfiles goes into the current directory instead with each Dockerfile suffixed with the release name. There is a new generate_dockerfiles_in_directories for the old behaviour.
Move slow ARM distribution out of the default distro list into Dockerfile_distro.slow_distros.
Add optional ?pin argument to dockerfile_distro generation to make it easier to customise version of packages installed.

Rearrange OCaml installation commands to be in Dockerfile instead of in Dockerfile_opam (which is now purely OPAM installation).
Create a ~/.ssh folder with the right permissions in all distros.
Ensure rsync is installed in all the Debian-based containers.
Correctly label the ARMv7 containers with the arch=armv7 label.
Use ppx to build instead of camlp4. Now depends on OCaml 4.02+.

Remove redundant apk update from Alpine definition.
Switch default cloud solver to one dedicated to these images so they can updated in sync (the default cloud one is getting hit by many bulk build hits in parallel and cannot cope with the load).
Add distro_of_tag and generate_dockerfile to Dockerfile_distro.
Add nano to images to satisfy opam pin going interactive.
Also include 4.03.0 flambda build.
Add ARMv7hf Raspbian distro (Wheezy and Jessie).

Add dev-repo metadata to OPAM file.
Add support for installing the cloud solver for platforms where aspcud is not available.
Add CMD entrypoints for containers.
Alpine: add bash in container (requested by @justincormack)
Debian: correct non-interactive typos and add dialog in container
Remove onbuild triggers from OPAM containers as it inhibits caching (suggestion via @talex5)
Include specific Debian versions (v7,8,9) in addition to the stable/unstable streams.
Add Dockerfile.crunch to reduce the number of layers by combining repeated RUN commands.
Set Debian apt-get commands to noninteractive.
Add support for Ubuntu 12.04 LTS and also bleeding edge 16.04.
Add sexplib convertors for Dockerfile.t.
Add Dockerfile_distro module to handle supported online distributions.
Add Dockerfile.label to support Docker 1.6 metadata labels.
Add generate_dockerfiles_in_git_branches to make it easier to use Docker Hub dynamic branch support to build all permutations.
Correctly escape the run_exec, entrypoint_exec and cmd_exec JSON arrays so that the strings are quoted.
Run yum clean after a Yum installation.
Add support for Alpine Linux.
Cleanup OPAM build directory to save container space after building from source.
Remove support for OpenSUSE remotes, as it is no longer maintained.

Add Dockerfile_opam and Dockerfile_opam_cmdliner modules with specific rules for managing OPAM installations with Dockerfiles.