Enable shellcheck and fix warnings (heroku#123)

.github/workflows/ci.yml

@@ -23,3 +23,12 @@ jobs:
         uses: actions/checkout@v4
       - name: Functional tests on heroku:${{ matrix.stack_number }}-build
         run: test/run
+
+  shell-lint:
+    runs-on: ubuntu-22.04
+    container:
+      image: koalaman/shellcheck-alpine:v0.9.0
+    steps:
+      - uses: actions/checkout@v4
+      - name: shellcheck
+        run: shellcheck -x bin/compile bin/detect bin/release bin/report

Makefile

@@ -1,5 +1,8 @@
 test: heroku-22-build heroku-20-build
 
+shellcheck:
+	@shellcheck -x bin/compile bin/detect bin/release bin/report
+
 heroku-22-build:
 	@echo "Running tests in docker (heroku-22-build)..."
 	@docker run -v $(shell pwd):/buildpack:ro --rm -it -e "STACK=heroku-22" heroku/heroku:22-build bash -c 'cp -r /buildpack /buildpack_test; cd /buildpack_test/; test/run;'

bin/compile

@@ -94,7 +94,7 @@ for PACKAGE in $(cat $BUILD_DIR/$APT_FILE_MANIFEST | grep -v -s -e '^#' | grep -
     topic "Fetching .debs for $PACKAGE"
     apt-get "${APT_OPTIONS[@]}" -y "${APT_FORCE_YES[@]}" -d install --reinstall "$PACKAGE" | indent
   fi
-done
+done < <(grep --invert-match -e "^#" -e "^\s*$" -e "^:repo:" "${BUILD_DIR}/Aptfile")
 
 mkdir -p "$BUILD_DIR/.apt"