Add automated install and stable updates

update.sh

@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+set -Eeuo pipefail
+
+SCRIPT_PATH="${BASH_SOURCE[0]:-$0}"
+SCRIPT_DIR="$(cd "$(dirname -- "$SCRIPT_PATH")" && pwd -P)"
+cd "$SCRIPT_DIR"
+
+usage() {
+  cat <<'USAGE'
+用法：
+  ./update.sh [branch-or-tag]
+
+说明：
+  - 不带参数时，默认更新 stable 分支
+  - 带参数时，可以切换到指定分支或 tag
+  - 更新后会自动执行一次 ./backup.sh --dry-run 自检
+USAGE
+}
+
+if [[ "${1:-}" == "-h" || "${1:-}" == "--help" ]]; then
+  usage
+  exit 0
+fi
+
+need_cmd() {
+  command -v "$1" >/dev/null 2>&1 || {
+    echo "缺少命令：$1" >&2
+    exit 2
+  }
+}
+
+need_cmd git
+need_cmd bash
+
+TARGET_REF="${1:-}"
+if [[ -z "$TARGET_REF" ]]; then
+  TARGET_REF="stable"
+fi
+
+git fetch --tags origin
+
+if git show-ref --verify --quiet "refs/tags/${TARGET_REF}"; then
+  git checkout "${TARGET_REF}"
+else
+  git checkout "${TARGET_REF}"
+  git pull --ff-only origin "${TARGET_REF}"
+fi
+
+chmod 755 \
+  "${SCRIPT_DIR}/backup.sh" \
+  "${SCRIPT_DIR}/clean_backups.sh" \
+  "${SCRIPT_DIR}/lib/telegram.sh" \
+  "${SCRIPT_DIR}/install.sh" \
+  "${SCRIPT_DIR}/update.sh"
+
+bash "${SCRIPT_DIR}/backup.sh" --dry-run