Add cabal-gild, a cabal formatter (#361)

Author: jian-lin

README.md

@@ -221,7 +221,7 @@ functions.
 <!-- `> bash ./supported-programs.sh` -->
 
 <!-- BEGIN mdsh -->
-`treefmt-nix` currently supports 107 formatters:
+`treefmt-nix` currently supports 108 formatters:
 
 * [actionlint](programs/actionlint.nix)
 * [alejandra](programs/alejandra.nix)
@@ -232,6 +232,7 @@ functions.
 * [buf](programs/buf.nix)
 * [buildifier](programs/buildifier.nix)
 * [cabal-fmt](programs/cabal-fmt.nix)
+* [cabal-gild](programs/cabal-gild.nix)
 * [clang-format](programs/clang-format.nix)
 * [cljfmt](programs/cljfmt.nix)
 * [cmake-format](programs/cmake-format.nix)

examples/formatter-cabal-gild.toml

@@ -0,0 +1,6 @@
+# Example generated by ../examples.sh
+[formatter.cabal-gild]
+command = "cabal-gild-wrapper"
+excludes = []
+includes = ["*.cabal", "cabal.project", "cabal.project.local"]
+options = []

programs/cabal-gild.nix

@@ -0,0 +1,44 @@
+{
+  mkFormatterModule,
+  lib,
+  config,
+  pkgs,
+  ...
+}:
+
+let
+  cfg = config.programs.cabal-gild;
+in
+{
+  meta.maintainers = [ ];
+
+  imports = [
+    (mkFormatterModule {
+      name = "cabal-gild";
+      package = [
+        "haskellPackages"
+        "cabal-gild"
+      ];
+      includes = [
+        "*.cabal"
+        "cabal.project"
+        "cabal.project.local"
+      ];
+    })
+  ];
+
+  config = lib.mkIf cfg.enable {
+    settings.formatter.cabal-gild = {
+      # cabal-gild doesn't support multiple file targets
+      # https://github.com/tfausak/cabal-gild/issues/35
+      command = pkgs.writeShellApplication {
+        name = "cabal-gild-wrapper";
+        text = ''
+          for file in "$@"; do
+            ${lib.getExe cfg.package} --io="$file"
+          done
+        '';
+      };
+    };
+  };
+}