tools: add a script to pull from upstream repos into the subtrees

tools/pull-upstream.sh

@@ -0,0 +1,26 @@
+#!/bin/sh
+REPO="${1}"
+REF="${2}"
+DIR=""
+
+usage() {
+    printf "usage: $0 <server|webapp> <ref>\n" 1>&2
+    printf "ref: main, tag, branch or commit hash\n" 1>&2
+    exit 1
+}
+
+case "$REPO" in
+    server)
+        REPO="https://github.com/etesync/server.git"
+        DIR="server"
+        ;;
+    webapp)
+        REPO="https://github.com/etesync/etesync-web.git"
+        DIR="webapp"
+        ;;
+    *) usage;;
+esac
+[ -z "${REF}" ] && usage
+
+cd $(dirname $0)/..
+exec git subtree pull -P "${DIR}" "${REPO}" "${REF}"