Add fallback Git remote for updates

update.sh

@@ -4,6 +4,12 @@ set -Eeuo pipefail
 SCRIPT_PATH="${BASH_SOURCE[0]:-$0}"
 SCRIPT_DIR="$(cd "$(dirname -- "$SCRIPT_PATH")" && pwd -P)"
 cd "$SCRIPT_DIR"
+CONF_FILE="${SCRIPT_DIR}/env.conf"
+
+if [[ -f "$CONF_FILE" ]]; then
+  # shellcheck disable=SC1090
+  source "$CONF_FILE"
+fi
 
 usage() {
   cat <<'USAGE'
@@ -13,6 +19,7 @@ usage() {
 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
+  - 默认从 origin 更新；如果失败且配置了 GIT_REMOTE_FALLBACK，则自动回退到备用仓库
 USAGE
 }
 
@@ -32,17 +39,46 @@ need_cmd git
 need_cmd bash
 
 TARGET_REF="${1:-}"
+UPDATE_SOURCE="origin"
 if [[ -z "$TARGET_REF" ]]; then
   TARGET_REF="stable"
 fi
 
-git fetch --tags origin
+fetch_from_origin() {
+  git fetch --tags origin
+}
+
+fetch_from_fallback() {
+  [[ -n "${GIT_REMOTE_FALLBACK:-}" ]] || return 1
+  git fetch --tags "${GIT_REMOTE_FALLBACK}" \
+    "+refs/heads/*:refs/remotes/fallback/*" \
+    "+refs/tags/*:refs/tags/*"
+}
+
+if fetch_from_origin; then
+  UPDATE_SOURCE="origin"
+elif fetch_from_fallback; then
+  UPDATE_SOURCE="fallback"
+  echo "origin 更新失败，已回退到备用仓库：${GIT_REMOTE_FALLBACK}"
+else
+  echo "更新失败：origin 不可用，且备用仓库也不可用" >&2
+  exit 2
+fi
 
 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}"
+  if ! git show-ref --verify --quiet "refs/remotes/${UPDATE_SOURCE}/${TARGET_REF}"; then
+    echo "未找到目标分支：${TARGET_REF}（来源：${UPDATE_SOURCE}）" >&2
+    exit 2
+  fi
+
+  if git show-ref --verify --quiet "refs/heads/${TARGET_REF}"; then
+    git checkout "${TARGET_REF}"
+    git merge --ff-only "refs/remotes/${UPDATE_SOURCE}/${TARGET_REF}"
+  else
+    git checkout -B "${TARGET_REF}" "refs/remotes/${UPDATE_SOURCE}/${TARGET_REF}"
+  fi
 fi
 
 chmod 755 \