Boost tarball release that works with CMake

From: Mojca Miklavec (mojca.miklavec.lists_at_[hidden])
Date: 2022-11-16 01:35:45

Dear developers,

For a CMake-based project we need to fetch Boost sources as part of
the build process (unless boost is already installed, in which case
that version can be used).

We are using CMake's FetchContent that recursively clones the
repository from GitHub, but that process is extremely slow. On the
Windows runner in GitHub actions it takes roughly 3 extra minutes to
"git clone" boost alone (or 11 minutes for something like "choco
install boost-msvc-14.3"). I tried to fetch the .7z file instead, but
that one doesn't work because the CMake support gets stripped from the
distributed sources when generating the tarballs.

A single file would result in a much faster and more reliable
workflow. The file can be cached on GitHub Actions, on a local
computer one doesn't need to repeatedly clone the repository (which
also slows down other parts of CMake) etc.

I started the discussion here:
    https://github.com/boostorg/release-tools/pull/35
where it has been explained to me that:
- either the CMake support needs to be heavily refactored (unlikely to
happen soon)
- or the project could generate one tarball using the layout that's
consistent with git repository

The second option might eventually be fulfilled automatically by
GitHub, but that is probably not likely to happen any time soon
either.

I can imagine that creating one extra '.tar.xz' with a slightly
different layout to support CMake builds might be straightforward to
make.

Is there any chance to fulfill my dream to be able to build a boost
tarball with CMake out-of-the-box?

Thank you very much,
    Mojca