dev meeting 20230823

Present: @rgrinberg @gridbugs @rikusilvola @rjbou @Leonidas-from-XIV

Multiple OPAM repos

@rgrinberg talked to @dra27 about how opam will deal with repos in the future and it looks like it will be just git going forward
We can do git-only before OPAM does, since we don't need to keep support for existing users
We need support for multiple repos
- How to support multiple forks of the same repo?
- Maybe keep all repos as remotes in a single repo to avoid duplication if people have the same repo forked? Then use git archive to materialize the files for the solver
- Repos set in dune-workspace file, with priorities
Remove our existing HTTP support

@gridbugs PR is going to yield nicer to read lock files, since it basically mirrors the OPAM filtering support so the translation is 1:1
@Alizter PR is a more general solution, but the files would look rather convoluted. case and cond can also be added later

For Unix builds we can just concatenate paths and be done, but Windows only support limited length environment variables and thus search paths
For Windows we'd need to create simpler folders with all in one folder in the file system and add that to the search path
@rjbou asks whether we expect to require Cygwin
- We do require some Unix environment with tools like git, curl, a compiler, but it can be anything. We don't install any system tools.
- MSVC is not supported on OCaml 5 again yet