Updated fourmolu script

.github/format.sh

@@ -1,5 +1,6 @@
 #!/bin/bash
 
-nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/refs/tags/21.05.tar.gz \
-          -p haskellPackages.fourmolu \
-          --run 'make format_check'
+# Extensions necessary to tell fourmolu about 
+EXTENSIONS="-o -XTypeApplications -o -XTemplateHaskell -o -XImportQualifiedPost -o -XPatternSynonyms -o -fplugin=RecordDotPreprocessor"
+SOURCES=$(git ls-tree -r HEAD --full-tree --name-only | grep -E '.*\.hs')
+~/.local/bin/fourmolu --mode check --check-idempotence $EXTENSIONS $SOURCES