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+# Tree-sitter Grammars
+
+Use [grammar-sources.nix](grammar-sources.nix) to define tree-sitter grammars sources.
+
+Tree-sitter grammars follow a common form for compatibility with the [`tree-sitter` CLI](https://tree-sitter.github.io/tree-sitter/cli/index.html).
+This uniformity enables consistent packaging through shared tooling.
+
+## Adding a Grammar
+
+To declare a new package, map the language name to a set of metadata required for the build.
+At a minimum, this must include the `version` and `src`.
+
+You may use a shorthand [flakeref](https://nix.dev/manual/nix/2.24/command-ref/new-cli/nix3-flake#url-like-syntax) style `url` and `hash` for concise declarations.
+If the hash is not yet known, use a [fake hash placeholder](https://nixos.org/manual/nixpkgs/stable/#sec-pkgs-fetchers-updating-source-hashes).
+
+```nix
+{
+  latex = {
+    version = "0.42.0";
+    url = "github:vandelay-industries/tree-sitter-latex";
+    hash = "";
+  };
+}
+```
+
+This will expand to an element in `pkgs.tree-sitter.grammars` at build time:
+
+```nix
+{
+  tree-sitter-latex = {
+    language = "latex";
+    version = "0.42.0";
+    src = fetchFromGitHub {
+      owner = "vandelay-industries";
+      repo = "tree-sitter-latex";
+      ref = "v0.42.0";
+      hash = "";
+    };
+  };
+}
+```
+
+Each entry is passed to [buildGrammar](../build-grammar.nix), which in turn populates `pkgs.tree-sitter-grammars`.
+
+Attempt to build the new grammar: `nix-build -A tree-sitter-grammars.tree-sitter-latex`.
+This will fail due to the invalid hash.
+Review the downloaded source then update the source definition with the printed source `hash`.
+
+## Pinning Grammar Sources
+
+To pin to a specific ref, append this to the source `url` to override the default version tag.
+
+```nix
+{
+  latex = {
+    version = "0.42.0";
+    url = "github:vandelay-industries/tree-sitter-latex/ccfd77db0ed799b6c22c214fe9d2937f47bc8b34";
+    hash = "";
+  };
+}
+```
+
+This may be either a commit hash or tag.
+
+## Supported sources
+
+The `url` field supports the following prefixes:
+
+- `github:` → uses `fetchFromGitHub`
+- `gitlab:` → uses `fetchFromGitLab`
+- `sourcehut:` → uses `fetchFromSourcehut`
+
+To use [other fetchers](https://nixos.org/manual/nixpkgs/unstable/#chap-pkgs-fetchers), specify the `src` attribute directly:
+
+```nix
+{
+  foolang = {
+    version = "0.42.0";
+    src = fetchtorrent {
+      config = {
+        peer-limit-global = 100;
+      };
+      url = "magnet:?xt=urn:btih:dd8255ecdc7ca55fb0bbf81323d87062db1f6d1c";
+      hash = "";
+    };
+  };
+}
+```
+
+## Modifying Build Behaviour
+
+Additional attributes in the grammar definition are forwarded to `buildGrammar`, and then to `mkDerivation`.
+This includes build-related flags and metadata.
+
+```nix
+{
+  foolang = {
+    version = "1729.0.0";
+    url = "sourcehut:~example/tree-sitter-foolang";
+    hash = "";
+    generate = true;
+    meta = {
+      license = lib.licenses.mit;
+      maintainers = with lib.maintainers; [
+        kimburgess
+      ];
+    };
+  };
+}
+```
+
+## Updating
+
+All grammar sources have a default update script defined.
+To manually trigger an update of a specific grammar definition:
+
+```shell
+nix-shell maintainers/scripts/update.nix --argstr package tree-sitter-grammars.tree-sitter-${name}
+```
+
+Or, to update all grammars:
+
+```shell
+nix-shell maintainers/scripts/update.nix --argstr path tree-sitter-grammars --argstr keep-going true
+```
+