[new release] opam-monorepo (0.3.0)

[NathanReb]

Assemble and manage fully vendored Dune repositories

• Project page: https://github.com/ocamllabs/opam-monorepo
• Documentation: https://ocamllabs.github.io/opam-monorepo

CHANGES:

Added

• Add opam extensions x-opam-monorepo-opam-repositories and
  x-opam-monorepo-global-opam-vars to make lock fully reproducible.
  (Allow running a reproducible lock tarides/opam-monorepo#250, Fix explicit repo solver tarides/opam-monorepo#253, @NathanReb)
• Show an error message when the solver can't find any version that satisfies
  the requested version constraint in the user's OPAM file (Incorrect error message if attempting to lock a version that doesn't exist tarides/opam-monorepo#215, Better missing version error tarides/opam-monorepo#248, Relax ocaml compiler warning to allow ocaml-variants tarides/opam-monorepo#290
  @Leonidas-from-XIV)
• Allow packages to be marked as being provided by Opam and not to be pulled by
  opam-monorepo. To control this a new optional Opam file field,
  x-opam-monorepo-opam-provided is introduced. Its value is a list of package
  names that are to be excluded from being pulled (Allow marking certain packages as "installed via OPAM" tarides/opam-monorepo#234, @Leonidas-from-XIV)
• Show an error message when the OCaml version of the lock file does not match
  the OCaml version of the switch (Check the compiler version when pulling tarides/opam-monorepo#267, Check OCaml version of lockfile against the switch version tarides/opam-monorepo#268, @Leonidas-from-XIV)
• Generate a duniverse/README.md file to explain the basics of
  opam-monorepo in the vendored directory (Generate documentation in the duniverse/ folder tarides/opam-monorepo#272, Write a README.md when pulling a project tarides/opam-monorepo#274, @Leonidas-from-XIV)
• Add a --prefer-cross-compile flag for the solver to select cross-compiling
  versions of packages when available. This is determined through the presence
  of the "cross-compile" tag in the opam metadata.

Changed

• Bump lockfile version to 0.3 (Bump lockfile version and drop support for older lockfiles tarides/opam-monorepo#285, @NathanReb)
• Mark packages to be pulled by opam-monorepo with the vendor variable so
  using OPAM with opam install --deps-only --locked . will not install
  packages that will be installed with opam-monorepo pull (Vendor variable in lockfile tarides/opam-monorepo#237,
  @Leonidas-from-XIV)

Fixed

• Fix a bug where a package which had a single version that built with dune and got selected by the solver
  would be reported has having no version building with dune. (Only find candidates that can't be built if there is no solution tarides/opam-monorepo#245, @Leonidas-from-XIV)
• Fix the solver so it does not select beta versions of the compiler unless
  forced to by version constraints or --ocaml-version. (Prevent unecessary selection of beta versions tarides/opam-monorepo#269, @NathanReb)

Removed

• Drop support for lockfile versions 0.2 and lower (Bump lockfile version and drop support for older lockfiles tarides/opam-monorepo#285, @NathanReb)

[kit-ty-kate]

Thanks