Enforce shell linting/formatting and modernize scripts

.editorconfig

@@ -0,0 +1,38 @@
+# https://editorconfig.org
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_style = space
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.sh]
+binary_next_line = true
+# We use tabs in shell scripts since heredoc indent stripping (<<-) requires them:
+# https://www.gnu.org/software/bash/manual/html_node/Redirections.html#Here-Documents
+indent_style = tab
+shell_variant = bash
+switch_case_indent = true
+
+# Catches scripts without a .sh file extension, such as the Buildpack API scripts.
+[**/bin/**]
+binary_next_line = true
+indent_style = tab
+shell_variant = bash
+switch_case_indent = true
+
+# Catches sbin/ scripts without a .sh extension.
+[**/sbin/**]
+binary_next_line = true
+indent_style = tab
+shell_variant = bash
+switch_case_indent = true
+
+# Vendored third-party script that must not be modified.
+[test/shunit2.sh]
+ignore = true
+
+[Makefile]
+indent_style = tab

.github/workflows/ci.yml

@@ -10,7 +10,22 @@ on:
 permissions:
   contents: read
 
+env:
+  FORCE_COLOR: 1
+
 jobs:
+  lint:
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+      - name: Run ShellCheck
+        run: make lint-scripts
+      - name: Run shfmt
+        uses: docker://mvdan/shfmt:latest
+        with:
+          args: "--diff ."
+
   integration-test:
     runs-on: ubuntu-latest
     strategy:

.shellcheckrc

@@ -0,0 +1,2 @@
+# Enable all checks, including the optional ones that are off by default.
+enable=all

Makefile

@@ -1,4 +1,17 @@
-.PHONY: test test-parallel run run-ci publish
+.PHONY: lint lint-scripts check-format format test test-parallel run run-ci publish
+
+lint: lint-scripts check-format
+
+lint-scripts:
+	@git ls-files -z --cached --others --exclude-standard 'bin/*' 'sbin/*' '*.sh' \
+		| grep -zv '^test/shunit2\.sh$$' \
+		| xargs -0 shellcheck --check-sourced --color=always
+
+check-format:
+	@shfmt --diff .
+
+format:
+	@shfmt --write --list .
 
 STACK ?= heroku-24
 FIXTURE ?= test/fixtures/mod-basic-go126