Clarify project status in README

.github/workflows/check.yml

@@ -12,7 +12,13 @@ jobs:
       - uses: actions/checkout@v4
       - uses: DeterminateSystems/nix-installer-action@main
       - uses: DeterminateSystems/magic-nix-cache-action@main
+
       - name: Check Nix formatting
         run: |
-          nix shell "https://flakehub.com/f/NixOS/nixpkgs/*#nixpkgs-fmt" --command \
+          nix shell "https://flakehub.com/f/NixOS/nixpkgs/0.2405.636988#nixpkgs-fmt" --command \
             sh -c "git ls-files '*.nix' | xargs nixpkgs-fmt --check"
+
+      - name: Check links in README
+        run: |
+          nix shell "https://flakehub.com/f/NixOS/nixpkgs/0.2405.636988#lychee" --command \
+            lychee README.md

README.md

@@ -1,39 +1,80 @@
 # Flake schemas
 
+> [!NOTE]
+> Flake schemas are not yet supported in Nix.
+> You can track ongoing work in [this pull request][pr] against the upstream project.
+> Until that merges, you can [experiment with flake schemas](#experimenting-with-flake-schemas) using a candidate version of Nix.
+
 This [Nix flake][flakes] provides a set of schema definitions for commonly used flake output types.
 It's used by default for flakes that do not have a `schemas` output.
 
 It supports the following flake output types:
 
+* [`apps`][apps]
 * [`checks`][checks]
+* [`darwinConfigurations`][darwin]
+* [`darwinModules`][darwin]
 * [`devShells`][develop]
+* [`dockerImages`][docker]
+* [`formatter`][formatter]
+* [`homeConfigurations`][home]
+* [`homeModules`][home]
 * [`hydraJobs`][hydra]
 * [`legacyPackages`][legacy]
 * [`nixosConfigurations`][nixos]
 * [`nixosModules`][nixosmodules]
 * [`overlays`][overlays]
 * [`packages`][packages]
-* [`darwinConfigurations`][darwin]
-* [`darwinModules`][darwin]
-* [`homeConfigurations`][home]
-* [`homeModules`][home]
-* [`dockerImages`][docker]
 * `schemas`
+* [`templates`][templates]
+
+## Experimenting with flake schemas
+
+Flake schemas are not yet supported in Nix.
+To experiment with them, you can use the version of Nix from the [pull request][pr] to upstream.
+Here are some example commands, though please note that the first time you run one of these commands, you will build Nix in its entirety, which is resource instensive and could take a while:
+
+```shell
+# Display the flake schema for this repo
+nix run github:DeterminateSystems/nix-src/flake-schemas -- \
+  flake show "https://flakehub.com/f/DeterminateSystems/flake-schemas/*"
+
+# Display the flake schema for this repo as JSON
+nix run github:DeterminateSystems/nix-src/flake-schemas -- \
+  flake show --json "https://flakehub.com/f/DeterminateSystems/flake-schemas/*"
+
+# Display the flake schema for Nixpkgs
+nix run github:DeterminateSystems/nix-src/flake-schemas -- \
+  flake show "https://flakehub.com/f/NixOS/nixpkgs/*"
+
+# Display the flake schema for Nixpkgs as JSON
+nix run github:DeterminateSystems/nix-src/flake-schemas -- \
+  flake show --json "https://flakehub.com/f/NixOS/nixpkgs/*"
+```
 
 ## Read more
 
-- [Flake schemas: Making flake outputs extensible][blog] — blog post introducing flake schemas.
+- [Flake schemas: Making flake outputs extensible][blog] — the blog post introducing flake schemas.
+- [Flake schemas][video] — [Eelco Dolstra][eelco]'s talk on flake schemas at [NixCon 2023][nixcon-2023].
 
+[apps]: https://nix.dev/manual/nix/latest/command-ref/new-cli/nix3-run#apps
 [blog]: https://determinate.systems/posts/flake-schemas
+[branch]: https://github.com/DeterminateSystems/nix-src/tree/flake-schemas
 [checks]: https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-flake-check.html
 [darwin]: https://github.com/LnL7/nix-darwin
 [docker]: https://nixos.org/manual/nixpkgs/stable/#sec-pkgs-dockerTools
 [develop]: https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-develop.html
+[eelco]: https://determinate.systems/people/eelco-dolstra
 [flakes]: https://zero-to-nix.com/concepts/flakes
+[formatter]: https://nix.dev/manual/nix/latest/command-ref/new-cli/nix3-fmt
 [home]: https://github.com/nix-community/home-manager
 [hydra]: https://github.com/NixOS/hydra
 [legacy]: https://github.com/NixOS/nixpkgs/blob/d1eaf1acfce382f14d26d20e0a9342884f3127b0/flake.nix#L47-L56
+[nixcon-2023]: https://2023.nixcon.org
 [nixos]: https://github.com/NixOS/nixpkgs/tree/master/nixos
 [nixosmodules]: https://nixos.wiki/wiki/NixOS_modules
 [overlays]: https://nixos.wiki/wiki/Overlays
 [packages]: https://search.nixos.org/packages
+[pr]: https://github.com/NixOS/nix/pull/8892
+[templates]: https://nix.dev/manual/nix/latest/command-ref/new-cli/nix3-flake-init
+[video]: https://www.youtube.com/watch?v=ChaJY0V4ElM