ci: adopt nix flake and just-based quality checks (#15)

Brings http-codes.nvim in line with the rest of the Neovim plugin repos:

- Adds flake.nix with the standard dev shell (just, stylua, prettier,
selene, neovim, lua-language-server, vimdoc-language-server), using the
nixpkgs-packaged vimdoc-language-server rather than a custom flake
input.
- Adds a justfile with format/lint/ci recipes (nix fmt, stylua,
prettier, selene, lua-language-server, vimdoc-language-server) mirroring
the shared pattern.
- Replaces the multi-job quality workflow with a single Quality job that
runs `just format` and `just lint` inside the ci dev shell, and drops
the now-redundant ci.yaml workflow.

Author: barrettruth

.github/workflows/ci.yaml

@@ -7,83 +7,13 @@ on:
     branches: [main]
 
 jobs:
-  changes:
+  quality:
+    name: Quality
     runs-on: ubuntu-latest
-    outputs:
-      lua: ${{ steps.changes.outputs.lua }}
-      markdown: ${{ steps.changes.outputs.markdown }}
     steps:
       - uses: actions/checkout@v4
-      - uses: dorny/paths-filter@v3
-        id: changes
-        with:
-          filters: |
-            lua:
-              - 'lua/**'
-              - 'plugin/**'
-              - '*.lua'
-              - '.luarc.json'
-              - '*.toml'
-            markdown:
-              - '*.md'
-              - 'doc/**/*.md'
-
-  lua-format:
-    name: Lua Format Check
-    runs-on: ubuntu-latest
-    needs: changes
-    if: ${{ needs.changes.outputs.lua == 'true' }}
-    steps:
-      - uses: actions/checkout@v4
-      - uses: JohnnyMorganz/stylua-action@v4
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}
-          version: 2.1.0
-          args: --check .
-
-  lua-lint:
-    name: Lua Lint Check
-    runs-on: ubuntu-latest
-    needs: changes
-    if: ${{ needs.changes.outputs.lua == 'true' }}
-    steps:
-      - uses: actions/checkout@v4
-      - name: Lint with Selene
-        uses: NTBBloodbath/selene-action@v1.0.0
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}
-          args: --display-style quiet .
-
-  lua-typecheck:
-    name: Lua Type Check
-    runs-on: ubuntu-latest
-    needs: changes
-    if: ${{ needs.changes.outputs.lua == 'true' }}
-    steps:
-      - uses: actions/checkout@v4
-      - name: Run Lua LS Type Check
-        uses: mrcjkb/lua-typecheck-action@v0
-        with:
-          checklevel: Warning
-          directories: lua
-          configpath: .luarc.json
-
-  markdown-format:
-    name: Markdown Format Check
-    runs-on: ubuntu-latest
-    needs: changes
-    if: ${{ needs.changes.outputs.markdown == 'true' }}
-    steps:
-      - uses: actions/checkout@v4
-      - name: Setup pnpm
-        uses: pnpm/action-setup@v4
-        with:
-          version: 8
-      - name: Setup Node.js
-        uses: actions/setup-node@v4
-        with:
-          node-version: "20"
-      - name: Install prettier
-        run: pnpm add -g prettier@3.1.0
-      - name: Check markdown formatting with prettier
-        run: prettier --check .
+      - uses: cachix/install-nix-action@v31
+      - name: Format
+        run: nix develop .#ci --command just format
+      - name: Lint
+        run: nix develop .#ci --command just lint

.github/workflows/quality.yaml

@@ -0,0 +1,48 @@
+{
+  description = "http-codes.nvim — HTTP status code reference for Neovim";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    systems.url = "github:nix-systems/default";
+  };
+
+  outputs =
+    {
+      nixpkgs,
+      systems,
+      ...
+    }:
+    let
+      forEachSystem =
+        f: nixpkgs.lib.genAttrs (import systems) (system: f nixpkgs.legacyPackages.${system});
+    in
+    {
+      formatter = forEachSystem (pkgs: pkgs.nixfmt-tree);
+
+      devShells = forEachSystem (pkgs: {
+        default = pkgs.mkShell {
+          packages = [
+            pkgs.just
+            pkgs.prettier
+            pkgs.stylua
+            pkgs.neovim
+            pkgs.selene
+            pkgs.lua-language-server
+            pkgs.vimdoc-language-server
+          ];
+        };
+
+        ci = pkgs.mkShell {
+          packages = [
+            pkgs.just
+            pkgs.prettier
+            pkgs.stylua
+            pkgs.neovim
+            pkgs.selene
+            pkgs.lua-language-server
+            pkgs.vimdoc-language-server
+          ];
+        };
+      });
+    };
+}

flake.lock

@@ -0,0 +1,15 @@
+default:
+    @just --list
+
+format:
+    nix fmt -- --ci
+    stylua --check .
+    prettier --check .
+
+lint:
+    git ls-files '*.lua' | xargs selene --display-style quiet
+    lua-language-server --check . --configpath "$(pwd)/.luarc.json" --checklevel=Warning
+    vimdoc-language-server check doc/
+
+ci: format lint
+    @: