tree-sitter-grammars: pin rev for unstable grammars

lib.mapAttrs' (

  language: attrs:

  let

    source = lib.optionalAttrs (attrs ? url) (parseUrl attrs.url);

  in

  lib.nameValuePair "tree-sitter-${language}" (

    {

      # Default to the source attr name as the language

          if (isUnstable attrs.version) then

            [

              "--version"

              "branch"

              "branch${lib.optionalString (source ? ref) "=${source.ref}"}"

            ]

          else

            [

    // lib.optionalAttrs (attrs ? url && attrs ? hash) {

      src =

        let

          source = parseUrl attrs.url;

          fetch = lib.getAttr source.type {

            github = fetchFromGitHub;

            gitlab = fetchFromGitLab;

            codeberg = fetchFromCodeberg;

            # NOTE: include other types here as required

          };

          rev =

            if isUnstable attrs.version then

              attrs.rev

                or (throw "tree-sitter grammar '${language}': unstable version requires a pinned 'rev' attribute")

            else

              source.ref or "v${attrs.version}";

        in

        fetch {

          inherit (source)

            owner

            repo

            ;

          rev = source.ref or "v${attrs.version}";

          inherit rev;

          inherit (attrs) hash;

        };

    }

    // removeAttrs attrs [

      "url"

      "hash"

      "rev"

    ]

  )

) grammar-sources