nix-fmt: add command

tests/fmt.sh

@@ -0,0 +1,28 @@
+source common.sh
+
+set -o pipefail
+
+clearStore
+rm -rf $TEST_HOME/.cache $TEST_HOME/.config $TEST_HOME/.local
+
+cp ./simple.nix ./simple.builder.sh ./fmt.simple.sh ./config.nix $TEST_HOME
+
+cd $TEST_HOME
+
+nix fmt --help | grep "Format"
+
+cat << EOF > flake.nix
+{
+  outputs = _: {
+    formatter.$system = {
+      type = "app";
+      program = ./fmt.simple.sh;
+    };
+  };
+}
+EOF
+nix fmt ./file ./folder | grep 'Formatting: ./file ./folder'
+nix flake check
+nix flake show | grep -P 'x86_64-linux|x86_64-darwin'
+
+clearStore

tests/fmt.simple.sh

@@ -0,0 +1 @@
+echo Formatting: "${@}"

tests/local.mk

@@ -77,6 +77,7 @@ nix_tests = \
   post-hook.sh \
   function-trace.sh \
   flake-local-settings.sh \
+  fmt.sh \
   eval-store.sh \
   why-depends.sh \
   import-derivation.sh \