[alexadereyko]

Brief

The bundle takes one commit per layer (bundle.json), makes each layer available by FetchLayer, prebuilt from a
staging or from its sources, and packs installers. In CI it lays every layer's staging into its run, from the
registry or staged there when the registry lacks it, and assembles the installers from them.

Description

FetchLayer (cmake/FetchLayer.cmake, cmake/FetchLayer/), FetchContent for layers, knowing nothing of openDAQ:

• A layer (a repository at a revision) gives one or more stagings, each with its DEPENDS, its axes (triplet by
  default) and its identity: idx-<sha256> of the commits, pkg-<sha256> of those and the axes, the same as the
  registry's tags.
• FETCHLAYER_BUILD (NEVER | MISSING | ALWAYS, or per layer) picks a prebuilt staging from the store or the
  layer's sources; a prefix is imported, sources are added in one tree.
• cmake/Layers.cmake declares the layers, cmake/Packing.cmake and CPackOptions.cmake pack the stagings and
  components a package preset names (core, modules, installer).

CI (.github/workflows):

• bundle.yml: on a pull request, by hand or called; inputs replace a layer's commit from bundle.json. Runs
  resolve.yml, then assemble.yml.
• resolve.yml: resolves the commits and their channels, pulls the stagings the registry has, and stages a missing
  layer here by its own stage.yml, never published, on the bundle's platforms only (exclude-jobs); the core
  first, the modules against it. Every staging lands as <staging>-staging-<job>.
• assemble.yml: builds the installers (DEB, NSIS, productbuild) from those artifacts with no compiling, installs
  each as a user would and smoke-checks it (tests/installed, C++ and the C binding).

Usage example

Locally, from a filled store:

cmake --preset bundle-native
cmake --build --preset bundle-native
cpack --preset installer

A layer from its sources, the rest prebuilt: cmake --preset bundle-native -DFETCHLAYER_BUILD_OPCUAMODULES=ALWAYS.

In CI, a layer at another commit:

gh workflow run bundle.yml -R openDAQ/openDAQ-bundle -f opcua-modules=<sha | branch | tag>