Add the announcement for opam 2.3.0~alpha1

opam-2-3-0-alpha1.md

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+title: "opam 2.3.0 alpha1 release"
+authors: [
+  "Raja Boujbel - OCamlPro" {"mailto:raja.boujbel(à)ocamlpro.com"}
+  "Kate Deplaix - Ahrefs" {"mailto:kit-ty-kate(à)outlook.com"}
+  "David Allsopp - Tarides" {"mailto:david(à)tarides.com"}
+]
+date: "2024-09-19"
+--BODY--
+
+_Feedback on this post is welcomed on [Discuss](https://discuss.ocaml.org/t/ann-opam-2-3-0-alpha1/XXXXX)!_
+
+As mentioned in [our talk at the OCaml Workshop 2024](https://icfp24.sigplan.org/details/ocaml-2024-papers/10/Opam-2-2-and-beyond),
+we decided to switch to a time-based release cycle (every 6 months), starting with opam 2.3.
+
+As promised, we are happy to announce the first alpha release of opam 2.3.0.
+You can view the full list of changes in the
+[release note](https://github.com/ocaml/opam/releases/tag/2.3.0-alpha1).
+
+This version is an alpha, we invite users to test it to spot previously
+unnoticed bugs as we head towards the stable release.
+
+## Major breaking change
+
+When loading a repository, opam won't automatically populate the `extra-files:` field with the files found in the `files/` directory anymore.
+
+This is a breaking change and means that if you are using the `files/` directory without the `extra-files:` field, you need to make sure that every files in that directory are listed in the `extra-files` field.
+Once done the resulting opam file is backward-compatible and you don't need to worry about anything else.
+
+If you have an opam repository, you should make sure every files are listed so every packages continue to work without any issue.
+This can be done automatically using the `opam admin update-extrafiles` command.
+
+## Major changes
+
+* Silently mark packages requiring an unsupported version of opam as unavailable instead of raising an error. This means an opam repository can now allow smoother upgrade in the future where some packages can require a newer version of opam without having to fork the repository to upgrade every packages to that version like it was done for the upgrade from opam 1.2 to 2.0
+
+* Add a new `opam list --latests-only` option to only list the latest packages. Note that this option is sensible to the order they were given in the command line. For example: `--available --latests-only` will first list all the available packages, then choose only the latest packages in that set; while `--latests-only --available` will first lists all the latest packages, then only show the ones that are available in that set
+
+* Fix and improve `opam install --check`. That command now checks if the whole dependency tree of the package is installed instead of only the root dependencies
+
+* Add a new `--verbose-on` option to enable verbose mode on specified package names. *Thanks to [@desumn](https://github.com/desumn) for this contribution*
+
+* Add a new `opam switch import --deps-only` option to install only the dependencies of the root packages listed in the opam switch export file
+
+* `opam switch list-available` will now not display compilers flagged with `avoid-version`/`deprecated` unless `--all` is given
+
+* `opam switch create --repos` now accepts git URLs suffixed with `.git` instead of requiring the `git+https://` protocol prefix. This is consistant with other commands such as `opam repository add`. *Thanks to [@Keryan-dev](https://github.com/Keryan-dev) for this contribution*
+
+* `opam switch set-invariant` now returns the actual invariant syntax expected by `--invariant`
+
+* The `builtin-0install` solver was improved and should now be capable of being your default solver instead of `builtin-mccs+glpk`. It was previously mostly only suited for automated tasks such as Continuous Integration. If you wish to give it a try, simply call `opam option solver=builtin-0install`
+
+* Most unhelpful conflict messages were fixed
+
+* Fix the value of the `arch` variable when the current OS is 32bit on a 64bit machine
+
+* opam now fails when git submodules fails to update instead of showing a warning and ignoring the error
+
+* opam and its libraries are now available on Windows with OCaml >= 5.0
+
+Various performance and other improvements were made and bugs were fixed.
+API changes are denoted in the release note linked above.
+This release also includes a handful of PRs improving the documentation and more two dozen PRs improving and extending the tests.
+
+## Try it!
+
+The upgrade instructions are unchanged:
+
+1. Either from binaries: run
+
+For Unix systems
+```
+bash -c "sh <(curl -fsSL https://raw.githubusercontent.com/ocaml/opam/master/shell/install.sh) --version 2.3.0~alpha1"
+```
+or from PowerShell for Windows systems
+```
+Invoke-Expression "& { $(Invoke-RestMethod https://raw.githubusercontent.com/ocaml/opam/master/shell/install.ps1) } -Version 2.3.0~alpha1"
+```
+or download manually from [the Github "Releases" page](https://github.com/ocaml/opam/releases/tag/2.3.0-alpha1) to your PATH.
+
+2. Or from source, manually: see the instructions in the [README](https://github.com/ocaml/opam/tree/2.3.0-alpha1#compiling-this-repo).
+
+
+You should then run:
+```
+opam init --reinit -ni
+```
+
+
+Please report any issues to [the bug-tracker](https://github.com/ocaml/opam/issues).
+
+Happy hacking!