diff --git a/rosdistro.sh b/rosdistro.sh
new file mode 100755
index 0000000..bc8c260
--- /dev/null
+++ b/rosdistro.sh
@@ -0,0 +1,51 @@
+#!/bin/bash
+set -e
+
+git_option="git -c user.email=non-existence@tuna.tsinghua.edu.cn -c user.name=Noname"
+
+function repo_init() {
+        UPSTREAM="$1"
+        WORKING_DIR="$2"
+        git clone "$UPSTREAM" "$WORKING_DIR"
+}
+
+function update_git() {
+	UPSTREAM="$1"
+        repo_dir="$2"
+        cd "$repo_dir"
+        echo "==== SYNC $repo_dir START ===="
+	git remote set-url origin "$UPSTREAM"
+        /usr/bin/timeout -s INT 3600 git remote -v update -p
+	head=$(git remote show origin | awk '/HEAD branch:/ {print $NF}')
+	[[ -n "$head" ]] && echo "ref: refs/heads/$head" > HEAD
+        objs=$(find objects -type f | wc -l)
+        [[ "$objs" -gt 8 ]] && git repack -a -b -d
+        sz=$(git count-objects -v|grep -Po '(?<=size-pack: )\d+')
+        total_size=$(($total_size+1024*$sz))
+        echo "==== SYNC $repo_dir DONE ===="
+}
+
+function checkout_branch() {
+	repo_dir="$1"
+	work_tree="$2"
+	branch="$3"
+	echo "Checkout branch $branch to $work_tree"
+	if [[ ! -d "$2" ]]; then
+		$git_option clone "$repo_dir" --branch "$branch" --single-branch "$work_tree"
+	else
+		cd "$work_tree"
+		$git_option pull
+	fi
+}
+
+UPSTREAM_BASE=${TUNASYNC_UPSTREAM_URL:-"https://github.com/ros/rosdistro"}
+total_size=0
+
+if [[ ! -d "$TUNASYNC_WORKING_DIR/.git" ]]; then
+        echo "Initializing"
+        repo_init "${UPSTREAM_BASE}" "$TUNASYNC_WORKING_DIR"
+fi
+update_git "${UPSTREAM_BASE}" "$TUNASYNC_WORKING_DIR/.git"
+checkout_branch "$TUNASYNC_WORKING_DIR/.git" "$TUNASYNC_WORKING_DIR" "master"
+
+echo "Total size is" $(numfmt --to=iec $total_size)