Configure `apt.kitware.com` in the development container so that `cmake`
is the latest CMake release rather than the older one Ubuntu carries, and
so that developers reach each further release through `apt-get` alone.
Fetch the repository's signing key, verified against the hash the
`Dockerfile` pins, and trust it just long enough to install
`kitware-archive-keyring`, which then provides the key, so that `apt`
follows the rotations Kitware makes to it. Interpolating the hash into
the step that fetches the key also busts the build cache when the hash
changes, so a rotation is picked up rather than served from an old layer.
Reaching either the key or the repository needs `curl` and a certificate
store, neither of which the base image carries, so install them first.
Install `glab`, the GitLab CLI, and `glab-axi`, an agent-ergonomic
wrapper around it, in the development container.
Default `GITLAB_HOST` to `gitlab.kitware.com` so that both address our
GitLab instance without further configuration, persist the `glab`
configuration directory on a volume so that a credential need be created
only once, and pass a `GITLAB_TOKEN` or `GITLAB_CLIENT_ID` from the host
through to the container.
Neither tool can authenticate on its own, so check for a working
credential each time a tool attaches to the container and print what
remains to be set up if there is none.
Provide a `.devcontainer` definition, following the Dev Container
Specification, to give contributors a ready-made Linux environment with
the tools needed to build CMake, run its test suite, build its
documentation, and satisfy its style rules.
Base the container on Ubuntu, which offers the broadest ecosystem of
packages and tooling for development, including a recent `cmake` and the
`clang-format` version our style rules require, exactly. Mirror the
package lists of the Debian image our CI infrastructure uses, section by
section, so that the dependencies available closely match the ones
against which merge requests are tested. Build the image the way the
images under `.gitlab/ci/docker/` are built: bind mount the package
lists and the installation script rather than copying them in, and cache
the package lists and downloaded archives so that a rebuild fetches only
what has changed.
Run optional `.devcontainer/hooks/root.sh` and
`.devcontainer/hooks/user.sh` scripts, both ignored by Git, so that
developers may customize the container without modifying tracked files.
Document usage in a new `Help/dev/devcontainer.rst`.
Fixes: #28043
Taylor Braun-Jones