build: enforce portable line endings

scripts/verify-line-endings.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+if [[ $# -gt 1 ]]; then
+  echo "usage: $0 [root]" >&2
+  exit 2
+fi
+
+if [[ $# -eq 1 ]]; then
+  root="$1"
+  fixture_mode=true
+else
+  root="$(git rev-parse --show-toplevel)"
+  fixture_mode=false
+fi
+
+if [[ ! -d "$root" ]]; then
+  echo "not a directory: $root" >&2
+  exit 2
+fi
+
+root="$(cd "$root" && pwd)"
+offenders=()
+
+while IFS= read -r -d '' file; do
+  if LC_ALL=C grep -Il $'\r' "$file" >/dev/null; then
+    offenders+=("${file#"$root"/}")
+  fi
+done < <(
+  if [[ "$fixture_mode" == true ]]; then
+    find "$root" -type f -print0
+  else
+    git -C "$root" ls-files -z | while IFS= read -r -d '' path; do
+      printf '%s\0' "$root/$path"
+    done
+  fi
+)
+
+if (( ${#offenders[@]} )); then
+  printf '%s\n' "CRLF line endings detected:" >&2
+  printf '%s\n' "${offenders[@]}" >&2
+  exit 1
+fi