update-scripts/version-info: get channel status for supported versions

Fetch channel info from NixOS/infra, the canonical source of truth.

(cherry picked from commit 9328f4437d)

update-scripts/version-info/supported-versions.nix

@@ -0,0 +1,62 @@
+{
+  system ? builtins.currentSystem,
+  pkgs ? import <nixpkgs> { inherit system; },
+  lib ? import <nixpkgs/lib>,
+  channelsJSON ? throw "Neither `channels` or `channelsJSON` provided",
+  channels ? builtins.fromJSON channelsJSON,
+}:
+let
+  # Pick out supported stable channels
+  supported = [
+    "beta"
+    "stable"
+    "deprecated"
+  ];
+
+  stable_versions =
+    channels.channels
+    |> builtins.mapAttrs (channel: entry: entry // { inherit channel; })
+    |> builtins.attrValues
+    |> builtins.filter (entry: entry.variant or null == "primary")
+    |> builtins.filter (entry: builtins.elem entry.status supported)
+    |> builtins.map (entry: {
+      name = entry.channel |> builtins.match "nixos-(.+)" |> builtins.head;
+      value = {
+        inherit (entry) channel status;
+        # Currently, Nixvim stable branches match NixOS channel names
+        branch = entry.channel;
+      };
+    })
+    |> builtins.listToAttrs;
+
+  newest_stable =
+    stable_versions |> builtins.attrNames |> builtins.sort (a: b: a > b) |> builtins.head;
+
+  bumpYear = y: toString (lib.toIntBase10 y + 1);
+  bumpMonth =
+    m:
+    assert m == "05" || m == "11";
+    if m == "05" then "11" else "05";
+
+  unstable =
+    newest_stable
+    |> builtins.match "(.+)[.](.+)"
+    |> (v: {
+      y = builtins.elemAt v 0;
+      m = builtins.elemAt v 1;
+    })
+    |> (v: {
+      y = if v.m == "11" then bumpYear v.y else v.y;
+      m = bumpMonth v.m;
+    })
+    |> (v: "${v.y}.${v.m}");
+in
+pkgs.writers.writeTOML "channels.toml" {
+  versions = stable_versions // {
+    ${unstable} = {
+      branch = "main";
+      channel = "nixpkgs-unstable";
+      status = "rolling";
+    };
+  };
+}