feat: add lint task, check for required stages

refs #9

Makefile

@@ -32,6 +32,10 @@ all: \
 compat:
 	./src/compat.sh
 
+.PHONY: lint
+lint:
+	./src/lint.sh
+
 .PHONY: preseed
 preseed:
 	./src/preseed.sh

src/lint.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+set -eu
+
+has-stage () {
+  grep -rnw ./packages/*/Containerfile -e "^FROM.*${1}$" | awk -F"/" '{ print $3 }' | sort
+}
+
+check-stages () {
+  all_packages=$(ls -1 ./packages | sort)
+
+  stages="base fetch build install test package"
+
+  for stage in $stages; do
+    missing=$(comm -13 <(has-stage "${stage}") <(ls -1 ./packages | sort))
+    if [ $(printf "${missing}" | wc -l) -gt "0" ]; then
+      echo "${missing}" | xargs printf "%s is missing '${stage}' stage\n"
+    fi
+  done
+
+}
+
+check-stages