maintainers: add script and workflows to check sortedness

the script can output a list of sed commands to create the order it
expects to find. this was mainly useful for initially sorting the list,
but we'll keep it here for later reference.

Co-authored-by: Jörg Thalheim <Mic92@users.noreply.github.com>

.github/workflows/check-maintainers-sorted.yaml

@@ -0,0 +1,21 @@
+name: "Check that maintainer list is sorted"
+
+on:
+  pull_request:
+    paths:
+      - 'maintainers/maintainer-list.nix'
+permissions:
+  contents: read
+
+jobs:
+  nixos:
+    runs-on: ubuntu-latest
+    if: github.repository_owner == 'NixOS'
+    steps:
+      - uses: actions/checkout@v3
+      - uses: cachix/install-nix-action@v19
+        with:
+          # explicitly enable sandbox
+          extra_nix_config: sandbox = true
+      - name: Check that maintainer-list.nix is sorted
+        run: nix-instantiate --eval maintainers/scripts/check-maintainers-sorted.nix

maintainers/scripts/check-maintainers-sorted.nix

@@ -0,0 +1,57 @@
+let
+  lib = import ../../lib;
+  inherit (lib)
+    add attrNames elemAt foldl' genList length replaceStrings sort toLower trace;
+
+  maintainers = import ../maintainer-list.nix;
+  simplify = replaceStrings [ "-" "_" ] [ "" "" ];
+  compare = a: b: simplify (toLower a) < simplify (toLower b);
+  namesSorted =
+    sort
+      (a: b: a.key < b.key)
+      (map
+        (n: let pos = builtins.unsafeGetAttrPos n maintainers;
+            in assert pos == null -> throw "maintainers entry ${n} is malformed";
+              { name = n; line = pos.line; key = toLower (simplify n); })
+        (attrNames maintainers));
+  before = { name, line, key }:
+    foldl'
+      (acc: n: if n.key < key && (acc == null || n.key > acc.key) then n else acc)
+      null
+      namesSorted;
+  errors = foldl' add 0
+    (map
+      (i: let a = elemAt namesSorted i;
+              b = elemAt namesSorted (i + 1);
+              lim = let t = before a; in if t == null then "the initial {" else t.name;
+          in if a.line >= b.line
+             then trace
+               ("maintainer ${a.name} (line ${toString a.line}) should be listed "
+                + "after ${lim}, not after ${b.name} (line ${toString b.line})")
+               1
+             else 0)
+      (genList (i: i) (length namesSorted - 1)));
+in
+assert errors == 0; "all good!"
+
+# generate edit commands to sort the list.
+# may everything following the last current entry (closing } ff) in the wrong place
+# with lib;
+# concatStringsSep
+#   "\n"
+#   (let first = foldl' (acc: n: if n.line < acc then n.line else acc) 999999999 namesSorted;
+#        commands = map
+#          (i: let e = elemAt namesSorted i;
+#                  begin = foldl'
+#                    (acc: n: if n.line < e.line && n.line > acc then n.line else acc)
+#                    1
+#                    namesSorted;
+#                  end =
+#                    foldl' (acc: n: if n.line > e.line && n.line < acc then n.line else acc)
+#                      999999999
+#                      namesSorted;
+#              in "${toString e.line},${toString (end - 1)} p")
+#          (genList (i: i) (length namesSorted));
+#    in map
+#      (c: "sed -ne '${c}' maintainers/maintainer-list.nix")
+#      ([ "1,${toString (first - 1)} p" ] ++ commands))