Add linters for metal and infra

Makefile

@@ -24,3 +24,7 @@ docs:
 
 .PHONY: apply
 apply: metal infra apps
+
+lint:
+	make -C metal lint
+	make -C infra lint

infra/Makefile

@@ -16,3 +16,6 @@ apply: plan
 
 destroy:
 	terraform destroy
+
+lint:
+	terraform fmt -recursive -diff -check

metal/Makefile

@@ -11,3 +11,6 @@ shutdown:
 	ansible-playbook \
 		--inventory hosts.yml \
 		shutdown.yml
+
+lint:
+	ansible-lint --project-dir .

tools/Dockerfile

@@ -5,6 +5,8 @@ COPY ./mirrorlist /etc/pacman.d/mirrorlist
 
 RUN yes | pacman --sync --refresh \
         ansible \
+        ansible-lint \
+        diffutils \
         docker \
         docker-compose \
         git \