Add shell lint script

scripts/lint-shell.sh

@@ -0,0 +1,211 @@
+#!/usr/bin/env bash
+#
+# Lint shell scripts in this repository.
+#
+# Usage:
+#   scripts/lint-shell.sh [--all] [--format] [--strict] [file ...]
+#
+# By default, runs ShellCheck and shell syntax checks on changed shell scripts.
+# Use --format to format with shfmt before linting. Use --all for the full tracked
+# baseline, or pass files explicitly to lint a smaller set.
+set -euo pipefail
+
+usage() {
+  sed -n '2,9p' "$0" | sed 's/^# \{0,1\}//'
+}
+
+die() {
+  echo "error: $*" >&2
+  exit 1
+}
+
+require_tool() {
+  command -v "$1" >/dev/null 2>&1 || die "required tool '$1' is not on PATH"
+}
+
+is_shell_file() {
+  local path="$1"
+  local first_line=""
+
+  [[ -f "$path" ]] || return 1
+
+  case "$path" in
+    *.sh)
+      return 0
+      ;;
+  esac
+
+  IFS= read -r first_line <"$path" || true
+  [[ "$first_line" =~ ^#!.*[/[:space:]](bash|dash|ksh|sh)([[:space:]]|$) ]]
+}
+
+ensure_git_work_tree() {
+  git rev-parse --is-inside-work-tree >/dev/null 2>&1 \
+    || die "run this from inside a git work tree, or pass files explicitly"
+}
+
+add_shell_file() {
+  local path
+  local existing
+
+  path="$1"
+  if ! is_shell_file "$path"; then
+    return 0
+  fi
+
+  if [[ "${#files[@]}" -gt 0 ]]; then
+    for existing in "${files[@]}"; do
+      if [[ "$existing" == "$path" ]]; then
+        return 0
+      fi
+    done
+  fi
+
+  files+=("$path")
+}
+
+collect_all_shell_files() {
+  local path
+
+  ensure_git_work_tree
+
+  while IFS= read -r -d '' path; do
+    add_shell_file "$path"
+  done < <(git ls-files -z)
+}
+
+collect_changed_shell_files() {
+  local path
+
+  ensure_git_work_tree
+
+  if git rev-parse --verify HEAD >/dev/null 2>&1; then
+    while IFS= read -r -d '' path; do
+      add_shell_file "$path"
+    done < <(git diff --name-only -z --diff-filter=ACMR HEAD)
+
+    while IFS= read -r -d '' path; do
+      add_shell_file "$path"
+    done < <(git diff --cached --name-only -z --diff-filter=ACMR)
+  else
+    collect_all_shell_files
+  fi
+
+  while IFS= read -r -d '' path; do
+    add_shell_file "$path"
+  done < <(git ls-files --others --exclude-standard -z)
+}
+
+collect_requested_shell_files() {
+  local path
+
+  for path in "$@"; do
+    add_shell_file "$path"
+  done
+}
+
+syntax_shell_for() {
+  local path="$1"
+  local first_line=""
+
+  IFS= read -r first_line <"$path" || true
+
+  case "$first_line" in
+    *"/sh"* | *" env sh"* | *"/dash"* | *" env dash"*)
+      printf 'sh'
+      ;;
+    *)
+      printf 'bash'
+      ;;
+  esac
+}
+
+run_syntax_checks() {
+  local file
+  local shell_name
+
+  for file in "$@"; do
+    shell_name="$(syntax_shell_for "$file")"
+    case "$shell_name" in
+      sh)
+        sh -n "$file"
+        ;;
+      bash)
+        bash -n "$file"
+        ;;
+      *)
+        die "unsupported shell for syntax check: $shell_name"
+        ;;
+    esac
+  done
+}
+
+format=false
+strict=false
+all=false
+requested_files=()
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    --all)
+      all=true
+      ;;
+    --format)
+      format=true
+      ;;
+    --strict)
+      strict=true
+      ;;
+    -h | --help)
+      usage
+      exit 0
+      ;;
+    --)
+      shift
+      requested_files+=("$@")
+      break
+      ;;
+    -*)
+      die "unknown option: $1"
+      ;;
+    *)
+      requested_files+=("$1")
+      ;;
+  esac
+  shift
+done
+
+require_tool shellcheck
+if [[ "$format" == true ]]; then
+  require_tool shfmt
+fi
+
+files=()
+if [[ "${#requested_files[@]}" -gt 0 ]]; then
+  collect_requested_shell_files "${requested_files[@]}"
+elif [[ "$all" == true ]]; then
+  collect_all_shell_files
+else
+  collect_changed_shell_files
+fi
+
+if [[ "${#files[@]}" -eq 0 ]]; then
+  echo "No shell files found."
+  exit 0
+fi
+
+if [[ "$format" == true ]]; then
+  echo "Formatting ${#files[@]} shell files"
+  shfmt_args=(-i 2 -ci -bn)
+  shfmt "${shfmt_args[@]}" -w "${files[@]}"
+fi
+
+echo "Linting ${#files[@]} shell files"
+
+shellcheck_args=(--severity=warning --external-sources --source-path=SCRIPTDIR)
+if [[ "$strict" == true ]]; then
+  shellcheck_args+=("--enable=check-extra-masked-returns,check-set-e-suppressed,quote-safe-variables,deprecate-which,avoid-nullary-conditions")
+fi
+
+shellcheck "${shellcheck_args[@]}" "${files[@]}"
+run_syntax_checks "${files[@]}"